++++=comment lines that were not in print version
*page=page number of original printed version (e.g., page 115=*115), so to
search for p. 115, search for *115.
++++ start of p. *60 in SOO 6 (S6c.htm) | Contents | Index | References
-------------------------------------------------- Common Name Scientific Name -------------------------------------------------- INVERTEBRATES crab, Dungeness Cancer magister crab, red rock C. productus squid Loligo opalescens FISH albacore Thunnus alalunga anchovy, northern Engraulis mordax bass, smallmouth Micropterus dolomieni bass, striped Morone saxatilis cod, Pacific Gadus macrocephalus croaker, white Genyonemus lineatus dogfish, spiny Squalus acanthias flounder, starry Platichthys stellatus hake, Pacific Merluccius productus herring, Pacific Clupea harengus pallasi lamprey, Pacific Lampetra tridentatus lamprey, river L. ayresi lingcod Ophiodon elongatus mackerel, jack Trachurus symmetricus perch, yellow Perca flavescens pollock, walleye Theragra chalcogramma rockfish, black Sebastes melanops sablefish Anoplopoma fimbria salmon, Atlantic Salmo salar salmon, chinook Oncorhynchus tshawytscha salmon, chum O. keta salmon, coho O. kisutch sanddab, Pacific Citharichthys sordidus sculpin, buffalo Enophrys bison sculpin, Pac. staghorn Leptocottus armatus shark, blue Prionace glauca shark, soupfin Galeorhinus zyopterus shark, thresher Alopias vulpinus sole, petrale Eopsetta jordani sole, sand Psettichthys melanostictus squawfish, northern Ptychocheilus oregonensis steelhead Salmo gairdneri sturgeon, white Acipenser transmontanus trout, brook Salvelinus fontinalis trout, cutthroat Salmo clarki walleye Stizostedion vitreum BIRDS Auklet, Rhinoceros Cerorhinca monocerata Brant Branta bernicla Bufflehead Bucephala albeola Coot, American Fulica americana Cormorant, Brandt's Phalacrocrax penicillatus Cormorant, Double-crested P. auritus Cormorant, Great P. carbo Cormorant, Pelagic P. pelagicus Dowitcher, Short-billed Limnodromus griseus Duck, Harlequin Histrionicus histrionicus Duck, Ring-necked Aythya collaris Duck, Ruddy Oxyura jamaicensis Duck, Wood Aix sponsa Dunlin Calidris alpina Eagle, Bald Haliaeetus leucocephalus Egret, Great Casmerodius albus Falcon, Peregrine Falco peregrinus Gadwall Anas strepera goldeneye spp. Bucephala islandica/clangula Goose, Canada Branta canadensis Grebe, Horned Podiceps auritus Grebe, Red-necked P. grisegena Grebe, Western Aechmophorus occidentalis Guillemot, Pigeon Cepphus columba Gull, Bonaparte's Larus philadelphia Gull, Glaucous-winged L. glaucescens Gull, Heerman's L. heermanni Gull, Ring-billed L. delawarensis Gull, Western L. occidentalis Heron, Great Blue Ardea herodias Kingfisher, Belted Ceryle alcyon Kittiwake, Black-legged Rissa tridactyla Knot, Red Calidris canutus Loon, Common Gavia immer Loon, Pacific G. pacifica Loon, Red-throated G. stellata Mallard Anas platyrhynchos Merganser, Common Mergus merganser Merganser, Hooded Lophodytes cucullatus Merganser, Red-breasted M. serrator Merlin Falco columbarius Murre, Common Uria aalge Murrelet, Ancient Synthliboramphus antiquus Murrelet, Marbled Brachyramphus marmoratus Osprey Pandion haliaetus Owl, Spotted Strix occidentalis Pelican, Brown Pelecanus occidentalis Pintail, Northern Anas acuta Plover, Semipalmated Charadrius semipalmatus Puffin, Tufted Fratercula cirrhata Sandpiper, Least Calidris minutilla Sandpiper, Western C. mauri scaup spp. Aythya marila/affinis Scaup, Greater A. marila Scoter, Black Melanitta nigra Scoter, Surf M. perspicillata Scoter, White-winged M. fusca Shearwater, Short-tailed Puffinus tenuirostris Shearwater, Sooty P. griseus Shoveler, Northern Anas clypeata Teal, Green-winged Anas crecca Tern, Arctic Sterna paradisaea Tern, Caspian S. caspia Tern, Common S. hirundo Turnstone, Ruddy Arenaria interpres Whimbrel Numenius phaeopus wigeon spp. Anas americana/penelope Yellowlegs, Greater Tringa melanoleuca MAMMALS dolphin, Pac. white-sided Lagenorhynchus obliquidens otter, river Lutra canadensis porpoise, Dall's Phocoenoides dalli porpoise, harbor Phocoena phocoena seal, elephant Mirounga angustirostris seal, harbor Phoca vitulina sea lion, California Zalophus californianus sea lion, northern Eumatopias jubatus
++++ start of p. *61 in SOO 6 (S6c.htm) | Contents | Index | References
II-A. INTRODUCTION------------------------------------------------------61
II-B. STAGE I MORTALITY: VULNERABILITY OF CURRENTLY RAISED HATCHERY
SMOLTS TO PREDATION SHORTLY AFTER RELEASE----------------------61
II-C. STAGE II MORTALITY: MORTALITY OF HATCHERY SMOLTS BECAUSE OF A
SYNERGISTIC RELATIONSHIP AMONG FOOD ABUNDANCE, INEFFICIENT
FEEDING, AND PREDATION-----------------------------------------61
***************************************************************************
Juvenile hatchery salmonids do not survive as well when released as do wild salmonids (Fraser 1974, Reisenbichler and McIntyre 1977, Gunsolus 1980, Dickson and MacCrimmon 1982, Ersbak and Haase 1983, Bachman 1984, Piggins and Mills 1985). The lowered survival of hatchery smolts appears to be because they are vulnerable to predation and/or because they may not feed efficiently enough to survive.
If the rearing of hatchery smolts was changed so that they could better adapt after release to feeding conditions and predators (see Chap. 4), hatchery smolts might not attract the predators that they now do, and cormorant predation might be less of an issue.
The two main sources of smolt mortality that have been suggested are limited food or predators (e.g., Pearcy 1988). These mortality factors are probably synergistic and should be considered for two separate time frames: Stage I (shortly after release when smolts are very naive, stressed, disoriented, and extremely vulnerable to predation) or Stage II (several days or more after release when smolts are less stressed, more wary, and less detectable by predators)(see Table II.1 at end of this Appendix).
Dividing the time of mortality into two Stages is important because the cause of mortality can differ between Stages. Further, it may be easier to improve the survival of smolts if the Stage when most mortality occurs can be resolved. Presently, there are no data to determine if most smolts die in Stage I or II or if most smolts that die in Stage I could have survived anyway (i.e., some may have been too small to survive, Mahnken et al. 1982, Parker and Stohr 1983, Wilson 1986, Mathews and Ishida 1989:1224, 1225).
Shortly after release, juvenile salmonids are stressed and disoriented because they have been forced into an unfamiliar environment (Macdonald et al. 1988). The stress of release can impair the ability of smolts to avoid predators or diminish their swimming abilities (e.g., Sylvester 1972, Coutant 1973, Sigismondi and Weber 1988).
Smolts may also have to adjust to salt water, which can make them act "sick" and impair their ability to escape predators. ODFW hatchery fish are reared in freshwater, so after they are released and move into estuaries, it may take about 100 hours for them to adapt to salt water; during this time they are physiologically stressed (Harry Wagner, ODFW Staff, oral testimony at the 20 April 1989 Work Session on House Bill 3185 before the House Committee on Agriculture, Forestry and Natural Resources). In contrast, private aquaculture smolts in Oregon are held in salt water for several days before being released, so that they don't have to adapt to increased salinities after release.
Recently released salmonids are easily detectable to predators because some smolts behave inappropriately in their new environment. Since hatchery salmonids are familiar only with feeding on pellets spread on the water surface, many smolts come to the surface to feed shortly after release and in so doing are easily seen by potential predators. Secondly, newly released smolts appear to often jump out of the water. Whatever the reason for their jumping, the result is that jumping makes them vulnerable to predators. For example, at Yaquina Estuary, I observed gulls sitting on the water catch and eat newly released smolts as they jumped near the gulls. A third way that salmonid juveniles act inappropriately is that they tend not to disperse after release, so that they remain in schools near the surface where they can be easily found and eaten by predators (Vincent 1960, Fresh 1983:74).
Recently released salmonids are particularly vulnerable to predation because they are also not wary of predators (e.g., Vincent 1960, Thompson 1966, Kanayama 1968, Fraser 1974, Patten 1975, 1977; Ginetz and Larkin 1976, Olla and Davis 1989, Suboski and Templeton 1989). Salmonid juveniles, however, may be capable of being trained to avoid predators (section 4-B-6), although this has not been attempted at hatcheries.
Since juvenile salmonids in hatcheries usually receive little exercise, their stamina appears to be less than for wild salmonids (e.g., L. S. Smith et al. 1983, 1985). This makes it more difficult for them to avoid predators and may impair their ability to feed and position themselves in the water column after release (Besner 1980, Besner and Smith 1983, L. S. Smith et al. 1983, 1985; Shchurov et al. 1986).
The combination of all these factors results in newly released hatchery smolts being vulnerable to predation. Thus, it is not surprising that a host of fish and bird predators in estuaries or the ocean (section 3-E) or in freshwater (e.g., northern squawfish, Brown and Moyle 1981, Buchanan et al. 1981; yellow perch, Dahle 1979; smallmouth bass, Nigro 1983, Pflug and Pauley 1984; and walleye, Nigro 1983, Maule and Horton 1984) that do not normally feed on juvenile salmonids may do so after hatchery releases.
After several days, smolts are much less vulnerable because once exposed to predators or predator models they can become more wary (Thompson 1966, Kanayama 1968, Patten 1975, 1977; Ginetz and Larkin 1976, Wood and Hand 1985,
++++ start of p. *62 in SOO 6 (S6c.htm) | Contents | Index | ReferencesOlla and Davis 1988, 1989; Suboski and Templeton 1989). Further, smolts apparently disperse so that they are not concentrated in schools near the surface; thus, predators can't detect them as easily.
Although Stage I mortality of some naive, hatchery smolts shortly after they are released may primarily be by predation; Stage II mortality factors may be synergistic and include inefficient feeding, a lack of food, and predation (Table II.1), especially in years with poor ocean conditions.
Below, problems that hatchery smolts have with feeding are discussed, and then the synergistic relationship between feeding and predation is examined.
Feeding of hatchery smolts may be impaired because they are unfamiliar with identifying and catching natural prey or because of increased physiological demands. Although not currently used, some methods of improving the ability of hatchery fish to feed after they are released are discussed in section 4-B-4.
PROBLEMS WITH PREY IDENTIFICATION AND PREY CAPTURE BY NEWLY RELEASED SMOLTS.--Since current hatchery salmonids are only familiar with eating pellets spread on top of a hatchery pond, it is understandable that they may have a problem shortly after release in finding natural food (e.g., Sosiak et al. 1979, Ersbak and Haase 1983, Bachman 1984, Kennedy et al. 1984, Suboski and Templeton 1989). This problem may be aggravated because hatchery fish position themselves higher in the water column than wild fish, so hatchery fish may not be located where appropriate prey are most abundant or are easiest to catch (e.g., Dickson and MacCrimmon 1982).
Some studies of salmonid smolts in aquaria have demonstrated that hatchery fish can quickly learn to catch natural prey (Paszkowski and Olla 1985, Stradmeyer and Thorpe 1987). But hatchery fish may do more poorly in the wild than these studies indicate because finding and catching sufficient prey to survive and prosper in the wild would be much more difficult than doing so in an aquarium (Stradmeyer and Thorpe 1987).
Identifying and catching prey clearly appears to be a problem for newly released chinook smolts. At Tillamook Bay and Yaquina Estuary, chinook smolts a week after release had stomachs that were much less full than those of wild smolts collected at the same time (Forsberg et al. 1975:26, Myers 1980:154). At Yaquina Estuary, Myers (1980:152) also found that stomachs of recently released chinook smolts often contained extraneous material such as pine needles, seeds, wood and paint chips, and pieces of plastic and styrofoam. At Puget Sound, L. S. Smith et al. (1970) found that recently released chinook smolts had little but pieces of wood or debris in their stomachs.
Coho smolts may not have as much difficulty in adapting to natural food. At Yaquina Estuary, Myers (1980:91) found that hatchery smolts were apparently quickly feeding on natural prey, but, at Siuslaw Estuary, Nicholas et al. (1979) found that most hatchery coho smolts had empty stomachs.
Studies of hatchery coho smolts in aquaria indicate that 69% can quickly identify and catch natural prey (Paszkowski and Olla 1985). But Paszkowski and Olla (1985) also found that the other 31% did not adapt and suggested that such a minority of nonadaptive smolts could contribute to the poor survival and feeding performance often reported for hatchery salmonids.
FEEDING INEFFICIENCY OF SMOLTS.--Hatchery smolts not only need to learn to identify and catch wild prey, they need to do so efficiently enough to at least maintain their body weight. Inefficient feeding has been a recognized problem for hatchery smolts (Ersbak and Haase 1983) that may be aggravated because hatchery fish may have higher energy and food demands than wild fish. For example, food requirements of recently released hatchery fish may be greater than for wild smolts because hatchery smolts are adapted to digesting food pellets and may not be able to efficiently digest natural food (Kennedy et al. 1984). Further, the basal metabolism of hatchery fish may be higher than for wild fish (Ersbak and Haase 1983), and hatchery fish may expend more energy in searching and catching prey than wild fish (e.g., Bachman 1984, Paszkowski and Olla 1985).
The length of time that it takes hatchery smolts to become as efficient in feeding as wild smolts is unclear and may differ among smolts (see Paszkowski and Olla 1985). For Atlantic salmon, some hatchery smolts took up to two months before they had the variety or amount of prey as wild smolts (Sosiak et al. 1979, Kennedy et al. 1984).
Food limitation, by itself, may not cause smolt mortalities because most smolt mortalities appear to occur within a few months or perhaps even within the first month after release (Gunsolus 1980, Pearcy 1988). In fact, death occurs in such a short time that starvation is probably not the proximate cause of mortality (Steve Johnson, ODFW Biologist, pers. comm.).
The growth, condition, and average stomach fullness of live smolts that were netted during years with poor upwelling conditions and poor smolt survival was similar to good upwelling years (Pearcy and Schoener 1987, Pearcy 1988). This would seem to indicate that smolts were adequately feeding. Unfortunately, data collected from smolts that were captured alive only provides information about the condition of surviving smolts, not those that died. Since the problem is to determine why smolts die during poor ocean conditions, data are needed about the health of smolts that died, not just the survivors.
It is probable that during the 1983 El Nino, when ocean upwelling conditions were poor for smolt survival, that food abundance for smolts may have been reduced. At least there was a major change in the diet of smolts in 1983 compared with other years (Pearcy et al. 1985, Pearcy and Schoener 1987). There are no data to determine if the prey used during the El Nino were as nutritious as normal prey; if they were not, then smolts would have to catch more prey to maintain themselves or grow.
Since hatchery smolts appear to be less adaptable in switching between available prey than wild fish (e.g., Sosiak et al. 1979, Ersbak and Haase 1983), hatchery smolts may have been particularly vulnerable during the El Nino when switching among prey may have been essential for survival. While some hatchery smolts might not have had much difficulty in switching, the 31% of
++++ start of p. *63 in SOO 6 (S6c.htm) | Contents | Index | Referenceshatchery coho smolts that were found to be nonadaptive feeders (Paszkowski and Olla 1985) may have been particularly hard-pressed. Thus, while studies such as Walters et al. (1978)(but see Peterson et al. 1982:849-850) suggest that there is much more food available for salmon smolts than they use, some or many hatchery smolts may not be able to take advantage of the abundance of food.
During poor upwelling conditions, many smolts (perhaps the 31% of Paszkowski and Olla 1985) may not eat sufficient food to maintain themselves or may also become susceptible to disease. Since predators are known to take weak or impaired prey (Curio 1976), these smolts may accordingly be very vulnerable to predation, especially since hungry hatchery coho juveniles expose themselves more to predators when they are hungry (Dill and Fraser 1984). Thus, food limitation because of either low prey abundance or inefficient smolt feeding may be the underlying, ultimate cause of death of many smolts in Stage II during poor ocean conditions, although predation may be the actual, proximate cause of death.
---------------------------------------------------------------------------TABLE II.1. Possible major causes of smolt mortality after release. It is assumed that fish are healthy when they are released, which may not always be the case (see Mace 1983); otherwise, Stage II mortality may also result from disease alone or in combination with predation. Note that these factors can be synergistic.
---------------------------------------------------------------------------
Synergistic Factors Causing
Time When Mortality Occurs Death of Smolts
---------------------------------------------------------------------------
Stage I Shortly After Release Stress of Handling *
Stress of Adapting to Salt Water *
Predation of Naive, Stressed
Smolts
Stage II Several Days Post-release Parr Reversion *
Feeding Inefficiency of Some
Smolts
Food Shortage
Predation
* Some private aquaculture coho smolts (e.g., 20-40%) appear to have been
released below their critical size for survival (Parker and Stohr
1983, Wilson 1986, Mathews and Ishida 1989:1224), so they may revert
to parr (Mahnken et al. 1982) and/or be vulnerable to other mortality
factors or disease.
---------------------------------------------------------------------------
++++ start of p. *64 in SOO 6 (S6c.htm) | Contents | Index | References
***************************************************************************
2000-| 1925-1988 OCEAN COMMERCIAL TROLL CATCH OF COHO
-|
T 1800-| X
H -| X
O 1600-| X X
U -| X X
S 1400-| X X
A -| X X
N 1200-| X X X X
D -| X XX X X
S 1000-| X XX X X
-| X 1988 XX XXXXX X
O 800-| X Level XXXX XXXXXXX X
F -| X X | X XXXXXXXXXXXXX XX X
600-|-----X-X-XX--------------------XX-----XXXXXXXXXXXXXXXXX-XX-----X
C -|XXX XX X XX XXXXX X XX XXXXXXXXXXXXXXXXXXXX XXX
O 400-|XXXXXXXXXXX XXXXX X XXX XXX XXXXXXXXXXXXXXXXXXXXXXX XXX
H -|XXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXX XXX
O 200-|XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
-|XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
0-|XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
|__________________________________________________________________
|****|****|****|****|****|****|****|****|****|****|****|****|****|
1930 1940 1950 1960 1970 1980 1990
---------------------------------------------------------------------------
---------------------------------------------------------------------------
APPENDIX III-B). Oregon ocean sports catches of coho for 1954-1988. Data are from K. Johnson (1983) and McQueen et al. (1988:40); 1988 preliminary data are from Laimons Osis (ODFW Biologist, pers. comm.).
1954-1988 OCEAN SPORTS CATCH OF COHO
-| X
480-| X
T -| X
H 440-| X
O -| X
U 400-| X
S -| X
A 360-| X
N -| X X
D 320-| X X X X X
S -| X X X X X
280-| 1988 X X X X X
O -| Level XX XXX XXX X X
F 240-| | X XXXXXXXXXX X X
-| -----------XXXXXXXXXXXX-X-X-----X-X
C 200-| XXXXXXXXXXXXXX XX X X
O -| XXXXXXXXXXXXXXXXXXXX XXXX
H 160 | XXXXXXXXXXXXXXXXXXXX XXXX
O -| X XXXXXXXXXXXXXXXXXXXXXX XXXX
120-| X XXXXXXXXXXXXXXXXXXXXXXXXXXX
-| XX XXXXXXXXXXXXXXXXXXXXXXXXXXX
80-| XX XXXXXXXXXXXXXXXXXXXXXXXXXXXX
-| XX XXXXXXXXXXXXXXXXXXXXXXXXXXXX
40-| XXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXX
-| XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
0-| XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
|_____________________________________________
|****|****|****|****|****|****|****|****|
50 55 60 65 70 75 80 85 90
++++ start of p. *65 in SOO 6 (S6c.htm) | Contents | Index | ReferencesAPPENDIX III-C). Oregon coastal stream sports catches of coho for 1966-1986. Data are from Berry (1981), K. Johnson (1983), and ODFW (1987); 1986 preliminary data are from Ron Williams (ODFW Biologist, pers. comm.). These data do not include the Columbia River or its tributaries.
-| 1966-1986 COASTAL STREAM SPORTS CATCH OF COHO
48-| X X
-| X X
44-| X X X
-| X X X
40-| X X X X
-| X X X X
34-| X X X X 1986
T -| X X X X LEVEL
H 32-| X X X X |
O -| X--X--X--X--X-----------------------------------------------X
U 28-| X X X X X X
S -| X X X X X X
A 24-| X X X X X X X
N -| X X X X X X X
D 20-| X X X X X X X X
S -| X X X X X X X X X
16-| X X X X X X X X X X X X X
O -| X X X X X X X X X X X X X X X X
F 12-| X X X X X X X X X X X X X X X X
-| X X X X X X X X X X X X X X X X X
C 8-| X X X X X X X X X X X X X X X X X X
O -| X X X X X X X X X X X X X X X X X X X
H 4-| X X X X X X X X X X X X X X X X X X X X
O -| X X X X X X X X X X X X X X X X X X X X X
0-| X X X X X X X X X X X X X X X X X X X X X
|________________________________________________________________
| * * * * | * * * * | * * * * | * * * * | *
1965 1970 1975 1980 1985
++++ start of p. *66 in SOO 6 (S6c.htm) | Contents | Index | References
***************************************************************************
T 600-| 1971-1988 OCEAN COMMERCIAL TROLL CATCH OF CHINOOK
H -|
O 540-| X
U -| X
S 480-| 1988 LEVEL X
A -| | X
N 420-| ---------------------------------------------X--X--X
D -| X X X
S 360-| X X X X
-| X X X X X
O 300-| X X X X X
F -| X X X X X
240-| X X X X X X X X X
C -| X X X X X X X X X X X X
H 180-| X X X X X X X X X X X X X
I -| X X X X X X X X X X X X X X
N 120-| X X X X X X X X X X X X X X X X
O -| X X X X X X X X X X X X X X X X
O 60-| X X X X X X X X X X X X X X X X X X
K -| X X X X X X X X X X X X X X X X X X
0-| X X X X X X X X X X X X X X X X X X
|_____________________________________________________________________
| * * * * | * * * * | * * * * | * * * * | * * *
1965 1970 1975 1980 1985
---------------------------------------------------------------------------
---------------------------------------------------------------------------
APPENDIX IV-B). Oregon ocean sports catches of chinook for 1966-1988. Data are from McQueen et al. (1988), and 1988 preliminary data are from Laimons Osis (ODFW Biologist, pers. comm.).
1966-1988 OCEAN SPORTS CATCH OF CHINOOK
T 80-| X
H -| X X
O 72-| X X
U -| X X
S 64-| X X
A -| X X X X X
N 56-| X X X X X X
D -| X X X X 1988 X X
S 48-| X X X X LEVEL X X
-| X X X X X X X | X X
O 40-| ---X--------X-----X--X-----X--X--X--------------X--------X-----X--X
F -| X X X X X X X X X X X X X
32-| X X X X X X X X X X X X X X X
C -| X X X X X X X X X X X X X X X X
H 24-| X X X X X X X X X X X X X X X X X X X X
I -| X X X X X X X X X X X X X X X X X X X X X X
N 16-| X X X X X X X X X X X X X X X X X X X X X X X
O -| X X X X X X X X X X X X X X X X X X X X X X X
O 8-| X X X X X X X X X X X X X X X X X X X X X X X
K -| X X X X X X X X X X X X X X X X X X X X X X X
0-| X X X X X X X X X X X X X X X X X X X X X X X
|______________________________________________________________________
| * * * * | * * * * | * * * * | * * * * | * * *
1965 1970 1975 1980 1985
++++ start of p. *67 in SOO 6 (S6c.htm) | Contents | Index | ReferencesAPPENDIX IV-C) Oregon coastal stream sports catches of chinook for 1970-1986. Data are from Berry (1981) and ODFW (1987); 1986 preliminary data are from Ron Williams (ODFW Biologist, pers. comm.). These data do not include the Columbia River or its tributaries. See IV-D) below for separate coastal stream catches for fall and spring chinook.
70-| 1970-1986 COASTAL STREAM SPORTS CATCH OF CHINOOK
-| X
65-| X
-| X
60-| X 1986
-| X X LEVEL
55-| X X |
T -| ------------------------X-----------------------X
H 50-| X X X X X
O -| X X X X X X
U 45-| X X X X X X X
S -| X X X X X X X
A 40-| X X X X X X X X
N -| X X X X X X X X X X X X X X
D 35-| X X X X X X X X X X X X X X X
S -| X X X X X X X X X X X X X X X X
30-| X X X X X X X X X X X X X X X X
O -| X X X X X X X X X X X X X X X X X
F 25-| X X X X X X X X X X X X X X X X X
-| X X X X X X X X X X X X X X X X X
C 20-| X X X X X X X X X X X X X X X X X
H -| X X X X X X X X X X X X X X X X X
I 15-| X X X X X X X X X X X X X X X X X
N -| X X X X X X X X X X X X X X X X X
O 10-| X X X X X X X X X X X X X X X X X
O -| X X X X X X X X X X X X X X X X X
K 5-| X X X X X X X X X X X X X X X X X
-| X X X X X X X X X X X X X X X X X
0-| X X X X X X X X X X X X X X X X X
|______________________________________________________________________
| * * * * | * * * * | * * * * | * * * * | * * *
1965 1970 1975 1980 1985
---------------------------------------------------------------------------
---------------------------------------------------------------------------
APPENDIX IV-D). Oregon coastal stream sports catches of fall or spring chinook for 1970-1986. Data are from Berry (1981) and ODFW (1987); preliminary 1986 data are from Ron Williams (ODFW Biologist, pers. comm.).
These data do not include the Columbia River or its tributaries.
1970-1986 COASTAL STREAM SPORTS CATCH OF FALL CHINOOK
48 |
-| FALL CHINOOK
44-| F 1986 LEVEL
T -| F |
H 40-| F-----------------------F-----------------------F
O -| F F F
U 36-| F F F F
S -| F F F F
A 32-| F F F F F F
N -| F F F F F F F F
D 28-| F F F F F F F F F
S -| F F F F F F F F F F
24-| F F F F F F F F F F F F F F
O -| F F F F F F F F F F F F F F F F
F 20-| F F F F F F F F F F F F F F F F F
-| F F F F F F F F F F F F F F F F F
C 16-| F F F F F F F F F F F F F F F F F
H -| F F F F F F F F F F F F F F F F F
I 12-| F F F F F F F F F F F F F F F F F
N -| F F F F F F F F F F F F F F F F F
O 8-| F F F F F F F F F F F F F F F F F
O -| F F F F F F F F F F F F F F F F F
K 4-| F F F F F F F F F F F F F F F F F
-| F F F F F F F F F F F F F F F F F
0-| F F F F F F F F F F F F F F F F F
|______________________________________________________________________
| * * * * | * * * * | * * * * | * * * * | * * *
1965 1970 1975 1980 1985
T 1970-1986 COASTAL STREAM SPORTS CATCH OF SPRING CHINOOK
H -|
O 28-| S
U -| S
S 24-| S
A -| S S S
N 20-| S S S
D -| S S S SPRING CHINOOK
S 16-| S S S S 1986 LEVEL
-| S S S S S S S S S S |
O 12-| S--S--S--S--S--S--S--S--S--S--S-----S-----------S
F -| S S S S S S S S S S S S S S S
8-| S S S S S S S S S S S S S S S
C -| S S S S S S S S S S S S S S S S S
H 4-| S S S S S S S S S S S S S S S S S
I -| S S S S S S S S S S S S S S S S S
N 0-| S S S S S S S S S S S S S S S S S
O |______________________________________________________________________
O | * * * * | * * * * | * * * * | * * * * | * * *
K 1965 1970 1975 1980 1985
++++ start of p. *68 in SOO 6 (S6c.htm) | Contents | Index | References
***************************************************************************
---------------------------------------------------------------------------
Brown Pelican... Common Loon..... Horned Grebe..........
1980 1982 1983 1979 1980 1981 1979 1980 1981 1984
---------------------------------------------------------------------------
April early 0 - - 39 39 42 65 52 86 134
late 0 0 0 24 49 31 55 71 67 72
May early 0 0 0 14 6 10 3 0 1 10
late 0 1 1 6 11 3 0 2 1 0
June early 0 8 84 - - - - - - -
late 20 59 27 0 8 - 0 - - -
---------------------------------------------------------------------------
---------------------------------------------------------------------------
Brant........... Bufflehead Caspian Tern..........
1981 1982 1984 1984 1985 1982 1983 1984 1985
---------------------------------------------------------------------------
April early 630 691 294 484 582 - - - 0
late 174 427 167 250 355 - - - 10
May early 12 67 206 58 17 - - - 0
late 0 2 9 0 0 - - - 16
June early 0 3 - - 0 19 30 28 9
late - - - - - 22 49 40 71
--------------------------------------------------------------------------
++++ start of p. *69 in SOO 6 (S6c.htm) | Contents | Index | References
***************************************************************************
------------------------------------------------------
Small Other
Whimbrel.. Shorebirds Shorebirds
1984 1985 1984 1985 1984 1985
-----------------------------------------------------
April early - 18 - 585 - 48
late 77 216 3800 2260 86 536
May early 150 172 4760 420 86 21
late 79 6 0 0 1 0
June early 18 9 0 0 3 0
late 23 - 0 - 3 -
-----------------------------------------------------
++++ start of p. *70 in SOO 6 (S6c.htm) | Contents | Index | References
*************************************************************************** VII-A. INTRODUCTION VII-B. STUDIES OF BIRD PREDATORS VII-C. STUDIES OF PREDATORY FISH ***************************************************************************
Research to determine that one species of animal or another can be a significant predator of smolts will not solve the predation problem. This is because a host of bird, fish, and marine mammal species have the potential to be significant predators (section 3-E). Even if one, two, or three species of predators were effectively stopped from preying on hatchery smolts, the remaining predators appear capable of taking the "saved" smolts because smolts may remain unwary of predators until after they are exposed to them (Ginetz and Larkin 1976, Patten 1977, Wood and Hand 1985, Olla and Davis 1988, 1989), whether that be in a river, estuary, or the ocean.
It should also be noted that additional research or studies will not solve the "predation" issue to the satisfaction of some fishermen unless the research shows that predators or potential predators should be controlled. Some fishermen "know" that predators are a problem, and no amount of research or scientific studies will convince them otherwise (e.g., Shotwell 1989). Thus, the only way that these fishermen will accept the results of these studies is if the results support their beliefs.
There have been ample studies in Oregon that have determined that Common Murres, cormorants, and other seabirds are predators of smolts (Matthews 1983, Ward 1983, Bayer 1986, Hoffman and Hall 1988). These studies did one or more of the following: count birds, observe birds to see if they were eating smolts, collect birds to determine how many smolts had been eaten, or use a bird's estimated daily food intake (see Appendix IX) to determine how many smolts could have been eaten. Based on the numbers of birds that can be present, the naiveness of hatchery smolts (Appendix II-B), and the number of smolts each bird can take, it is already clear that birds have the potential of eating many hatchery smolts.
There seems to be no point in doing more of these kinds of studies because they only provide very rough estimates of smolt predation. Since predators such as Common Murres and Brandt's Cormorants do not normally feed on smolts in Oregon (Scott 1973, Matthews 1983), these birds may clearly not feed on smolts every day. Further, it can not be reasonably assumed that all birds counted at a site where smolts could be present are eating only smolts because these birds may be eating other kinds of prey or may not be catching any smolts at all (section 2-F-14).
These kinds of studies also do not indicate the total number of birds that are feeding on smolts at a site because birds are coming and going at different times throughout the day. Thus, a census of birds at one time can inaccurately estimate the total number of individuals that may feed at a site throughout a day.
Studies to try to determine exactly how many smolts birds are eating is not currently possible. Such research would have to determine if individual birds are feeding throughout the day, every day, on hatchery smolts and how many smolts each individual bird is eating each day over a period of weeks or months. For this kind of research, significant numbers of birds have to be individually marked, each followed throughout a day for weeks to see where they are feeding, and the actual diet of each bird has to be determined each day without killing the bird. This kind of research is simply not possible with today's technology.
Although further research to simply determine that birds eat smolts in Oregon seems redundant, research to determine the potential significance of fish predators of smolts might be informative. Since fish predators have elsewhere been estimated to take 20-25% or more of smolts (Gunnerod et al. 1988), fish predators in Oregon may also be significant.
Preliminary observations in Oregon (e.g., Stuart 1984, Stuart and Buckman 1985) already indicate that at least adult coho salmon can be a significant predator of coho smolts (Nickelson 1986:533). But other predatory fish such as chinook, steelhead, cutthroat trout may also be significant smolt predators (section 3-E).
Studies using divers to observe fish predators of hatchery smolts in the days following a release (e.g., Anonymous 1959) could be helpful in discovering if smolts are vulnerable to predatory fish. Divers could work near the release site or at potential bottlenecks for smolt migration such as at a narrow mouth of an estuary.
Research to determine the stomach contents of predatory fish in estuaries or near the mouths of estuaries within 14 days after hatchery releases may also be valuable in establishing that predatory fish are eating smolts. This could be done by having ODFW salmon samplers or researchers check the stomach contents of salmon or predatory fish (e.g., black rockfish and lingcod) caught by fishermen and brought to public docks, marinas, charter boat docks, or dive shops to be gutted and cleaned. Since a major cost of research is to collect predatory fish, sampling fish brought in by fishermen could reduce research costs.
++++ start of p. *71 in SOO 6 (S6c.htm) | Contents | Index | References
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*************************************************************************** VIII-A. INTRODUCTION----------------------------------------------------71 VIII-B. DEFINITION OF "WILD" FISH---------------------------------------71 VIII-C. BENEFITS OF WILD SALMONIDS--------------------------------------71 VIII-D. HARMFUL EFFECTS OF HATCHERY SALMONIDS---------------------------71 ***************************************************************************
Wild fish stocks have not been prospering in recent years, and the number of spawning wild coho has been markedly declining in coastal streams and in the Columbia River and its tributaries (ODFW 1985a:5). Competition with hatchery fish appears to be one cause for the decline of wild stocks.
In spite of the possible deleterious effects of the hatchery fish, they are necessary to support these fisheries (Fresh 1983, ODFW 1985a). For example, in 1977-1982, hatchery coho accounted for about 75% of the ocean fishery off Oregon (Nickelson 1986:528).
Fishermen disagree about the management of wild salmon and steelhead. Some fishermen want the ODFW to abandon its current wild fish policy, so that the harvest rate could be increased and fishermen could thus catch more fish now, even though this would harm wild fish (see following VIII-D-4). Other fishermen and some fishing groups such as Oregon Trout recognize the importance of wild fish and feel that the ODFW should do more to protect wild fish (Bakke 1989). This conflict is another example of a no-win situation that the ODFW is stuck with (also see sections 2-B-1 and 6-D.
In the following sections, the benefits of wild stocks and then the harmful effects of hatchery stocks on wild fish are examined.
"Wild" fish can be variously defined. Three possible definitions include fish that have naturally spawned and reared in a given stream system:
1) for more than 10 generations. 2) for at least three generations (i.e., Type A wild fish in ODFW 1985a:4). 3) for one generation (i.e., Type B wild fish in ODFW 1985a:4).
Category #1 of wild fish includes the most pristine of native stocks adapted to a particular stream. Categories #2 and #3 can include progeny of hatchery fish brought in from distant non-native stocks. For example, natural spawning of non-native hatchery coho strays (i.e., adults not returning to their natal release site or hatchery), and their probable interbreeding with native coho in the Yaquina Basin has occurred for at least eight years (e.g., Nicholas et al. 1982, Nicholas and Van Dyke 1982, Jacobs 1988). Accordingly, it is doubtful if any pristine category #1 "wild" coho now exist in the Yaquina Basin, although category #2 and certainly #3 "wild" coho may be widespread.
In the following sections, "wild" fish refer to category #1 or #2 wild fish.
Although wild salmonids have aesthetic value and are also protected by law or policy (Dentler and Buchanan 1986), they are also important for more practical reasons. For example, wild fish don't cost taxpayers (including nonfishermen).
Secondly, wild salmonids produce proportionately more smolts than naturally spawning hatchery fish (Reisenbichler and McIntyre 1977, Chilcote et al. 1986, Bakke 1989).
Thirdly, juvenile hatchery salmonids do not survive as well after release as wild fish (Fraser 1974, Reisenbichler and McIntyre 1977, Gunsolus 1980, Dickson and MacCrimmon 1982, Ersbak and Haase 1983, Bachman 1984, Piggins and Mills 1985).
Fourthly, because of their genetic diversity and adaptation to the local conditions of a natal stream, wild fish may better withstand unfavorable environmental conditions, such as periods of low upwelling, than hatchery fish (Nickelson 1986). Thus, protecting wild fish to maintain their genetic diversity has been recognized to be important (Reisenbichler and McIntyre 1977, Stabell 1984, ODFW 1985a, L. S. Smith et al. 1985, Chilcote et al. 1986, Dentler and Buchanan 1986, Bakke 1989).
Fifthly, the ocean may also have a greater carrying capacity for wild than for hatchery fish because wild fish stocks are more genetically diverse (Parmenter and Bailey 1985). Thus, if wild fish stocks are further depleted, fisheries may subsequently decline.
Sixthly, wild salmon also benefit some fishermen because wild salmon distribute themselves more evenly along a stream (Dentler and Buchanan 1986), so that coastal stream anglers can have a better chance of fishing for them in solitiude. In contrast, fishermen for hatchery fish may have to fish "elbow to elbow" at sites near or below a hatchery where the fish were released and have subsequently returned (Dentler and Buchanan 1986).
Finally, wild salmonids are also useful as environmental indicators in detecting changes in water quality. Hatchery salmonids are not as suitable because they are less dependent on freshwater streams throughout their life (Dentler and Buchanan 1986).
Hatchery salmonid pre-smolts or smolts can compete with wild smolts for food, space, or shelter (Nicholas et al. 1979, Myers 1980, Myers and Horton 1982, Fresh 1983, Nicholas and Herring 1983). Such competition has been found to decrease the abundance of wild coho juveniles (Solazzi et al. 1983, ODFW 1985a:8, Johnson and Solazzi 1986, Nickelson et al. 1986). This competition can be increased if some private hatchery smolts migrate upstream into juvenile rearing areas, which has occurred (e.g., Jonasson 1983, Nicholas and Herring 1983).
To reduce such competition, releases into streams are regulated by the ODFW. Since some
++++ start of p. *72 in SOO 6 (S6c.htm) | Contents | Index | ReferencesSTEP volunteers exceeded their authority by becoming involved in cormorant harassment (section 1-E), one wonders if some STEP volunteers may have also released juvenile salmon at sites that they were not supposed to. Such unauthorized releases could harm wild fish stocks, perhaps irreparably (Nickelson 1981, Johnson and Solazzi 1986, Nickelson et al. 1986).
Wild juveniles spread themselves out more than hatchery fish (Fresh 1983), so when wild smolts migrate to the ocean they are not as conspicuous or as available to predators. In contrast, the conspicuousness, the naivete, and the abundance of mass releases of hatchery juveniles attract many predators that don't normally prey on salmonids (section 3-E and Appendix II-B). Once predators are attracted and form a "search image" for hatchery salmonids, they may also then prey on adjacent wild migrating juveniles. For example, in Ireland, Kennedy and Greer (1988) found that Great Cormorants preyed on hatchery and wild Atlantic salmon smolts.
Hatchery salmonids may also spread disease to wild salmonids (Dentler and Buchanan 1986). This could occur by the release of hatchery pre-smolts or smolts or by hatchery adults straying to spawn naturally.
Increasing fishing rates on hatchery salmon can also result in overharvesting wild salmon. Subsequently, too few wild salmon may escape to spawn, so that wild fish can't maintain their numbers (Gunsolus 1980, McGie 1984, Dentler and Buchanan 1986). Wild salmon may only be able to withstand a harvest rate of 67%, but harvest rates have been as high as 90% in 1976-1977 and 77-78% in 1981 and 1983 (Gunsolus 1980, ODFW 1985a:16).
Current opinion favors using hatchery stocks derived from native wild stocks. While this may help reduce genetic loss, there may still be some loss of genetic diversity because hatchery fish are selected for ease of rearing under hatchery conditions (Ersbak and Haase 1983). Thus, hatchery fish of the same stocks as wild fish generally show a reduction of genetic variation (Lindsay et al. 1988:4).
Hatchery smolts that return as adults but stray from their natal release site can create problems by competing with wild fish for limited spawning areas (Nicholas et al. 1982). Further, the natural spawning of hatchery strays can reduce the number of salmonids produced in streams because hatchery fish spawning naturally do not produce as many young as wild fish (Reisenbichler and McIntyre 1977, Chilcote et al. 1986, Bakke 1989).
Adult hatchery strays can also interbreed with wild fish and thus dilute the gene pool of the wild fish (Lindsey et al. 1988:4, Bakke 1989). This dilution is important because wild fish have evolved to be most efficient at spawning, growing, and returning to each local stream (Dentler and Buchanan 1986); such genetic dilution appears to be irreversible.
Adult straying, especially from some private hatcheries, can be significant. For example, beginning in the 1970's, private hatchery coho smolts were released into the Yaquina Basin and have recently been documented as constituting a significant percentage of all naturally spawning adult coho in the Yaquina (44% in 1980, 74% in 1981, and 91% in 1985)(Nicholas et al. 1982, Nicholas and Van Dyke 1982, Jacobs 1988).
Further, it was estimated that 73% of all naturally spawning coho in 1985 from the Salmon River at the southern border of Tillamook County to the Yachats River just north of the Siuslaw Estuary were from the private hatchery in the Yaquina Basin (Jacobs 1988). With hatchery fish constituting so many of the naturally spawning coho in the Yaquina Basin for so many years, it seems questionable if there are any genetically pure wild coho in the Yaquina Basin and perhaps also in other nearby coastal streams.
++++ start of p. *73 in SOO 6 (S6c.htm) | Contents | Index | References
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***************************************************************************
IX-A. INTRODUCTION------------------------------------------------------73
IX-B. DIGESTION CAN AFFECT PREY SIZE DETERMINATION----------------------73
IX-C. SHOOTING BIRDS AND USING STOMACH CONTENTS-------------------------73
IX-D. LIVE CAPTURE OF BIRDS AND USE OF STOMACH CONTENTS-----------------73
IX-E. USING PELLETS OR FECES TO DETERMINE DAILY FOOD CONSUMPTION--------74
IX-F. USING STOMACH CONTENTS OF BEACHED BIRDS---------------------------74
IX-G. DIRECT OBSERVATION OF FOOD EATEN BY WILD BIRDS--------------------74
IX-H. ESTIMATING DAILY FOOD CONSUMPTION OF WILD BIRDS FROM CAPTIVE
BIRDS----------------------------------------------------------74
IX-I. MEASURING ENERGY CONSUMPTION OF WILD BIRDS------------------------75
***************************************************************************
Although it may seem easy to determine how much food a bird eats daily, this, like so many other questions, is one that becomes more difficult as one more closely examines it. Currently, only estimates are available; these indicate that a fish-eating bird needs to eat an average of about 9-25% of its body weight daily (section 2-F-5). Cummings (1987) may also have estimated daily food intakes for Double-crested Cormorants, but I have not seen her thesis.
The various methods of estimating daily food consumption are briefly discussed below.
Several methods of determining daily food consumption involve analyzing the stomach contents of dead or live birds or examining bird pellets or feces.
Unfortunately, one problem common to all these methods is that a bird's digestion can impair a researcher's ability to determine all prey or prey sizes (e.g., Bowmaker 1963, Duffy and Jackson 1986:5-6). For example, fish may be partially digested, so that measuring prey size directly may not be possible. Further, some prey species may be entirely digested, so that they may be absent from a sample. For instance, birds can sometimes digest some fish within a few hours of ingestion (Bowmaker 1963, Jackson and Ryan 1986, Laugksch and Duffy 1986, Gales 1988). For a discussion of the digestion of fish by a cormorant, see Bowmaker (1963).
Oftentimes, prey species or size are determinable only from prey hard parts such as fish otoliths, fish eye crystals, or invertebrate hard parts such as squid beaks. The degree of digestion of fish otoliths or eye crystals may depend on meal size, prey species, prey size, and digestion time (Miller 1979:80, Duffy and Laurenson 1983, B. L. Furness et al. 1984, Duffy and Jackson 1986:6, Jackson and Ryan 1986, Furness and Monaghan 1987:24, Gales 1988).
If partially digested, otoliths can inaccurately estimate fish size (Duffy and Laurenson 1983, Gales 1988). For example, Gales (1988) found that prey size derived from otoliths can be significantly underestimated only 1-2 hours after ingestion and that some otoliths have been totally digested within one hour of ingestion.
If not all prey are found or if prey size can't be accurately determined, then it is not possible to accurately estimate the amount of food eaten. Thus, hardparts can only be used for determining relative diet and then only with caution.
Waterbirds have been shot and their stomach contents examined and weighed (e.g., Bowmaker 1963). Then each bird's daily food consumption has been estimated by using a multiplier factor to guess how much food would have been eaten in the rest of the day.
One problem with this procedure is that a multiplier factor is based on assumptions (e.g., that a bird would continue to eat at the same rate for the rest of the day). Since some waterbirds can eat at variable rates throughout the day or may only spend a few hours daily foraging and perhaps not eat the rest of the day (section 2-F-4); it is difficult to accurately use a bird's stomach contents to estimate how much it would have eaten the rest of the day. Further, part of the food may be partially digested so determination of prey species and size may be difficult (Appendix IX-B).
A second problem is that stomach contents may sometimes overestimate a bird's average daily food needs. For example, starved fish-eating birds can eat much more than average for 1-2 days and then not eat for a couple of days (section 2-F-5, "Maximum Smolts/Day").
The result is that shooting birds to determine their daily food consumption is unreliable (Mills 1967:383, Guillet and Furness 1985). However, stomachs of shot birds may be used to determine a bird's relative diet (e.g., Duffy and Jackson 1986:3).
Cormorants or other waterbirds may be most easily caught at nesting or roosting areas using slip nooses or traps (e.g., Tenaza 1966, Foster and Fitzgerald 1982, Duffy and Jackson 1986:3-4). Further, at Yaquina Estuary, I was once able to walk at night with the aid of only part of a flashlight beam and use only my hands in catching a Pelagic Cormorant that was roosting on rocks, so catching birds at night roosting areas can be successful.
At foraging areas, net guns have been used to catch waterfowl or Marbled Murrelets (Mechlin and Shaiffer 1980, Varoujean and Williams 1987:4). Although the use of tranquilizer guns to capture mammals is common, it is not a method mentioned for birds (Duffy and Jackson 1986:3- 4), perhaps because it may be too difficult to select a dose that doesn't harm a bird.
++++ start of p. *74 in SOO 6 (S6c.htm) | Contents | Index | References
Once caught, the preferable method for determining stomach contents appears to be using a stomach pump, not emetics that cause regurgitation (Wilson 1984, Duffy and Jackson 1986:4-5, Ryan and Jackson 1986, Gales 1987). Birds may also be physically forced to regurgitate (Pilon et al. 1983, Cooper 1985a, Craven and Lev 1987:66). An experienced worker can use a stomach pump to obtain nearly all stomach contents without killing a bird.
One problem with using stomach contents is that a bird may partially regurgitate before its stomach contents can be collected (Duffy and Jackson 1986:4). The main problem, though, is that it is unknown how much more food a bird would have eaten during the day, if it is caught early in the day; or how much food may have already been digested, if the bird is caught late in the day. Accordingly, stomach contents may reflect only what a bird has eaten recently.
Also, a bird's stomach contents may not be typical of its average daily food intake. For instance, starved fish-eating birds can eat much more than average for 1-2 days (e.g., section 2-F-5 "Maximum Smolts/Day).
The advantage to using pellets or feces is that they do not involve shooting or catching birds.
The major problem with using pellets and especially feces to determine the diet or daily food consumption of birds is that many hardparts may have been digested (Appendix IX-B).
Some birds, including cormorants, regurgitate pellets that may contain hard parts of fish (e.g., otoliths or eye crystals) or invertebrate prey (e.g., squid beaks)(Ainley et al. 1981, Duffy and Laurenson 1983, Pilon et al. 1983, Duffy and Jackson 1986:5, 6; Whitfield 1986, Craven and Lev 1987:66, Duffy et al. 1987b:830). One advantage to using pellets for cormorants is that it appears that they only cast about one pellet with food remains daily (Miller 1979:82, Duffy and Laurenson 1983).
Fish or invertebrate hard parts may also sometimes be found in bird feces (Duffy and Jackson 1986:5, 6). But waterbirds may defecate more than once daily at variable intervals (e.g., Great Blue Herons, Bayer unpubl. data), so it is not possible to relate a feces sample with how much a bird may have eaten daily. Further, prey hard parts are more likely to have been digested before being passed in feces than are prey hard parts found in bird stomachs or pellets, so many prey may not be represented in feces.
Some researchers have used birds found dead on beaches to estimate seabird diets (see Duffy and Jackson 1986:3). Since some of these seabirds may have been starving or most of their food may have been digested before death, prey remains may be overrepresentative of prey with exceedingly hard parts such as squid beaks (e.g., B. L. Furness et al. 1984). Another problem is that prey found in beached birds may not be typical of their normal diet (Duffy and Jackson 1986:3).
There are several major difficulties with estimating the daily food consumption of birds from observations of foraging birds.
Firstly, not all prey may be identified. Since many diving birds can swallow food underwater, not all prey may be observed. Further, even if observable, many prey may not be correctly identifiable (Cezilly and Wallace 1988).
Secondly, many fish-eating birds forage over large distances, so it can be logistically difficult for researchers to be always able to keep an individual bird under close enough observation during a day to observe all prey that it may catch and swallow. If a bird is a night-forager, making accurate estimates of prey are much more difficult, if not impossible.
Thirdly, if a bird is only closely watched for part of a day to determine what prey it catches, then the prey it may have eaten the rest of the day can only be grossly guessed. It can't be assumed that a bird will eat at a constant rate throughout the day because some fish-eating birds may forage mainly in the morning or for only a few hours daily (section 2-F-4).
Fourthly, since starved fish-eating birds can eat much more than average for 1-2 days (section 2-F-5, "Maximum Smolts/Day"), it is important that the daily food consumption of each bird be followed for several days. Food consumption during a single day may seriously over- or underestimate a bird's average daily food consumption. If following a bird for one day is difficult, following it for several days is even more so.
Finally, to determine daily food consumption by direct observations, it is essential that the size of prey be estimated accurately. Estimating prey size by comparison with bill length has been a common technique that has not received much critical evaluation. But, especially for large prey, using bill length may not be very accurate in determining prey length (Bayer 1985a). Errors in estimating prey length would be greatly magnified in estimating prey weight because the length-weight relationship is exponential (Bayer 1985a). Further, if prey vary greatly in body shapes, errors in prey identification, even if prey length is correctly estimated, may lead to gross errors in estimating prey weights (Bayer 1985a, Cezilly and Wallace 1988).
A common way of estimating daily food
++++ start of p. *75 in SOO 6 (S6c.htm) | Contents | Index | Referencesconsumptions of wild birds is to use food intakes or to measure metabolic rates of captive birds. Since captive birds aren't as mobile as wild birds, these measurements are then converted by use of various multiplicative factors to account for various types of locomotive activities or the estimated energetic cost of molting or nesting (Bowmaker 1963, Wiens and Scott 1975, Kendeigh et al. 1977, Ellis 1984, R. W. Furness 1984, Wiens 1984, Briggs and Chu 1987, Cummings 1987, Duffy and Siegfried 1987, Furness and Monaghan 1987).
To reasonably apply these methods to estimate the daily energetic requirements of wild birds, it is still necessary to observe wild birds to determine the typical duration of each type of activity (e.g., flying or diving), so that the energetic costs of each activity can be estimated (e.g., Kendeigh et al. 1977). Since daily metabolic rates can be influenced by ambient temperatures, weather, photoperiods, or a bird's energy-conserving activities; these factors must also be measured or included (Kendeigh et al. 1977, Wiens 1984, Furness and Monaghan 1987).
Once the daily energy requirements are estimated, then it is necessary to estimate the amount of food necessary to acquire this energy. This involves estimating conversion factors for prey live weights to dry weights and then dry weights to caloric content; these conversion factors can vary among prey (Dunn 1975, Marsault 1975, Wiens and Scott 1975:447, Swennen 1977:32, Duffy and Siegfried 1987). Then a bird's assimilation efficiency (which can also be variable) must be estimated to determine how much of the food's caloric content can be utilized in satisfying the bird's energetic demands (Dunn 1975, Kendeigh et al. 1977, Wiens 1984, Briggs and Chu 1987, Duffy and Siegfried 1987). With estimates at each stage of calculation, it is difficult to know how accurate the final estimated daily food consumption is.
With variability in prey caloric content, bird assimilation, and bird energetic needs, it is also clear that the amount of food eaten daily can vary (e.g., Marsault 1975). These sources of variation in daily food intake have, thus far, only received anecdotal consideration (e.g., Marsault 1975, Swennen 1977:32).
To avoid problems with using energy requirements of captive birds in estimating wild bird requirements, it has been proposed that the energy consumption rates of wild birds be measured directly by catching wild birds, inserting heart rate biotelemetry devices or radioisotopes, and releasing the birds to let them live normally (Kendeigh et al. 1977:199, R. W. Furness 1984:122, Furness and Monaghan 1987:75). If radioisotopes are used, then each bird has to be recaptured, and the isotope measured within a pre-determined length of time.
Even if these methods can be used, problems remain in converting the measured energy consumption into the amount of prey needed to be ingested daily because of variability in nutritive content of prey and variable bird assimilation rates (Appendix IX-H).
++++ start of p. *76 in SOO 6 (S6c.htm) | Contents | Index | References
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[A copy of the original typewritten letter is in the printed edition.]
***************************************************************************
[Paul Hanneman, Oregon House of Representatives letterhead]
February 21, 1989
Kathleen Confer
4905 Ellen Avenue
Tillamook, OR 97141
Dear Kathleen:
I'm sorry it has taken me until now to respond to your letter. I
wanted to let you know that we have introduced legislation which, if
approved, would allow the Oregon Department of Fish and Wildlife to
issue not more than three permits statewide during each of calendar
years 1989 and 1990 for hazing cormorants in inland waters.
The purpose of this bill is to provide some relief for downstream
migrating salmon during their four-week period. We suspect and
believe that we can prove that less than 50 percent of our expensive,
publicly-produced salmon and steelhead are able to reach the ocean.
The bill does not authorize anyone to physically harm the birds.
Thank you for your input and concern on this issue.
Very truly yours,
[signature]
Paul Hanneman
State Representative,
District 3
ph/ms
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[letterhead of U.S. Dept. of Agriculture, Animal and Plant Health
Inspection Service, Animal Damage Control, 727 N.E. 24th Avenue, Portland,
OR 97232]
Date: May 18, 1988
To: File
From: Thomas Hoffman, State Director
Thomas Hall, Wildlife Biologist
Subject: Tillamook Trip Report Regarding Smolt/Cormorant Problem
Since March 1985, Animal Damage Control has been involved in
cooperating with various private individuals in the Nehalem Bay
area assisting them in hazing cormorants feeding on salmon and
steelhead smolt. Participation has focused on the Nehalem River
system and the smolt produced in this area. Cooperators from the
Northwest Steelheaders Association and the Cooperative Salmon and
Trout Enhancement Projects (STEP) were provided technical
expertise and hazing supplies for scaring cormorants from smolt
vulnerable to depredation. Our past involvement evolved from our
previous fish-eating bird work with Federal and State fish
rearing facilites. The Oregon Department of Fish and Wildlife
(ODFW) was indirectly involved in 1985 and 1986 through contacts
with the North Fork Nehalem Fish Hatchery and State Fishery
Biologists.
On April 27, 1988 we (T. Hoffman and T. Hall) assisted
concerned cooperators in the Tillamook area by surveying the
problem of cormorant depredations and collecting a limited number
of birds to help understand the feeding habits of cormorants in
this tidal area. We collected 24 birds during the day at various
times to see differences in feeding behavior. All birds
collected were necropsied and grossly examined for esophageal and
gizzard contents. An observation of the number of birds using
the area was also determined. These observations will be
discussed, but first, background information will be given.
BACKGROUND
Most of the salmon and steelhead consumption by cormorants
occurs from March to May. During this time cormorants are
formidable predators and can consume large quantities of wild and
hatchery-reared fish. Although an estimate of smolt consumption
is unavailable, the percentage of smolt consumed is potentially
high.
Steelhead and salmon are vulnerable to predation their
entire lives. As smolts, predation vulnerability is much higher
as they are not "street-wise" and are of a size preferred by many
predators. Cormorants are potentially the most significant
predator to the smolt in the early stages, though several
predators are present, such as seals, herons, gulls, and murres.
Other predators are present in the ocean as well after they make
their transition from rivers to the sea. This toll plus natural
mortality greatly reduces the return of these anadromous fish.
++++ start of p. *78 in SOO 6 (S6c.htm) | Contents | Index |
++++2nd page of Hoffman and Hall ++++
It is hard to say which predator has the greatest impact on
the Nehalem and Tillamook salmon and steelhead, but cormorants
are the first in line to significantly feed on them and it is
easy to see they could potentially be a large problem. The
cormorants fly upstream to release sites and start feeding on the
smolt as they migrate toward the ocean. From here they follow
the schools downstream to the ocean. The fish take a few months
to complete this journey because they must acclimate to the
changing salinity levels. Therefore, depending on a few other
factors such as population size and time of release, cormorants
could have a significant impact on the population of smolt.
The primary cormorant that nests along the Oregon coast is
the Brandt's cormorant. Double-crested and pelagic also occur at
lower numbers. Brandt's cormorants are primarily restricted to
the coast. They nest in dense colonies on flat surfaces of rocky
islands. In 1979, the estimated population for Oregon was about
16,000. The double-crested cormorant population of coastal
regions in Oregon was estimated at 1700 birds. The pelagic
cormorant was found to be in much smaller groups scattered along
the coast and 6300 was the estimated population (correspondence
from USFWS).
TRIP RESULTS
From the Tillamook Bay area at the mouth of the Wilson,
Tillamook, and Trask rivers, 24 Brandt's cormorants were
collected on April 27, 1988. Of these 22 were adults and 2 were
immature. At 7:00 AM, 7 incoming (heading upriver) cormorants
were taken. Of these, 5 had no contents in their esophagus, 1
had 4 partially digested smolt, and 1 had 5. At 10:30 AM, 3
outgoing cormorants were collected with most fish in the
esophagus: 1 had 6 steelhead smolt (all 7-8"), 1 had 16 salmon
smolt, and 1 had 8 salmon smolt; and 7 incoming cormorants were
collected with only partially digested smolt in the gizzard: 1
had no smolt, 3 had 2 smolt, 2 had 4 smolt, and 1 had 5 smolt.
At 12:30 PM, 4 outgoing cormorants were collected with 4, 6, 7,
and 9 smolt in the esophagus and gizzard and 3 incoming
cormorants had 1, 3, and 3 smolt all partially digested. The
information from these collected birds suggests that birds begin
morning forays for food sometimes around 7:00 AM. The number of
fish consumed varied, but were greater for outgoing birds than
incoming suggesting they were consuming fish from up in the
rivers where the smolt were concentrated.
During the day, a flock of 250-300 birds was observed in the
bay along with several others seen at the same time in other
areas. A flock of 75 cormorants was hazed 0.5 miles upstream
from the mouth of the Tillamook River around 1:00 PM. No effort,
however, was made to determine cormorant numbers on the bay or in
the area.
++++ start of p. *79 in SOO 6 (S6c.htm) | Contents | Index | References
***************************************************************************
***************************************************************************
65th Oregon Legislative Assembly--1989 Regular Session
House Bill 3185
Sponsored by Representatives HANNEMAN, HANLON, SOWA, Senators BRADBURY,
BRENNEMAN at the request of Jim Erickson, Nehalem)
SUMMARY
The following summary is not prepared by the sponsors of the measure and is
not a part of the body thereof subject to consideration by the Legislative
Assembly. It is an editor's brief statement of the essential features of
the measure as introduced.
Directs State Fish and Wildlife Commission to issue only three
permits per year, in calendar years 1989 and 1990, for hazing of cormorants
on Oregon coastal rivers.
Declares emergency, effective on passage.
A BILL FOR AN ACT
Relating to cormorants; and declaring an emergency.
Be it Enacted by the People of the State of Oregon:
SECTION 1. Section 2 of this Act is added to and made a part of ORS
chapter 498.
SECTION 2. The commission, by rule, shall issue not more than three
permits in calendar year 1989 and not more than three permits in calendar
year 1990 for the hazing of cormorants (Phalacrocoracidae) on Oregon
coastal rivers. However, activities authorized by the permit shall not
include the killing, trapping or other taking of cormorants.
SECTION 3. This Act being necessary for the immediate preservation
of the public peace, health and safety, an emergency is declared to exist,
and this Act takes effect on its passage.
++++ start of p. *80 in SOO 6 (S6c.htm) | Contents | Index | References***************************************************************************
[The numbering of each line of text in the Bill is not included in the following transcription.]
***************************************************************************
65th Oregon Legislative Assembly--1989 Regular Session
A-Engrossed
House Bill 3185.
Ordered by the House April 26
Including House Amendments dated April 26
Sponsored by Representatives HANNEMAN, HANLON, SOWA, Senators BRADBURY,
BRENNEMAN at the request of Jim Erickson, Nehalem)
SUMMARY
The following summary is not prepared by the sponsors of the measure and is
not a part of the body thereof subject to consideration by the Legislative
Assembly. It is an editor's brief statement of the essential features of
the measure.
Directs State Fish and Wildlife Commission to issue only three
permits per year, in calendar years 1989 and 1990, for hazing of cormorants
on certain Oregon coastal rivers. Specifies time period for hazing.
Requires monitoring of activities and report to the Sixty-sixth Legislative
Assembly.
Declares emergency, effective on passage.
A BILL FOR AN ACT
Relating to cormorants; and declaring an emergency.
Be it Enacted by the People of the State of Oregon:
SECTION 1. Section 2 of this Act is added to and made a part of ORS
chapter 498.
SECTION 2. The commission, by rule, shall issue not more than three
permits in calendar year 1989 and not more than three permits in calendar
year 1990 for the hazing of cormorants (Phalacrocoracidae) on certain
Oregon coastal rivers. However, activities authorized by the permit shall
not include the killing, trapping or other taking of cormorants. Hazing
activities shall be conducted only on rivers that flow into Nehalem Bay or
Tillamook Bay, during the period between release of hatchery smolts and
June 30. Hazing activities shall be monitored by the Department. A log of
activities shall be kept and a report made to the Sixty-sixth Legislative
Assembly.
SECTION 3. This Act being necessary for the immediate preservation
of the public peace, health and safety, an emergency is declared to exist,
and this Act takes effect on its passage.
++++ start of p. *81 in SOO 6 (S6c.htm) | Contents | Index | References***************************************************************************
[Verbatim transcription of typed one-page letter. A photocopy of the original is in the paper edition.]
***************************************************************************
April 24, 1989
Randy Fisher
Director of O.D.F.&W.
We would like to submit this petition to the O.D.F.&W. Commission to
issue Cormorant hazing permits for the Nehalem and Tillamook Bays.
The purpose of the hazing was well argued at the House Ag. committee
meeting in Salem and all sides came to the agreement, hazing is necessary to
protect the smolts if a carefully monitored program is carried out. Every-
body except O.D.F.&W.
Wwould like to petition the commission for Cormorant harassment permits
as soon as possible. The reason being the smolts are coming down the river
and are being eaten up by the Cormorants at an astounding rate.
We request at least 6 permits for the Nehalem and Tillamook Bays
consisting of 2 master permits to J.R. Erickson and Sam Gallino with
4 sub-permits to be issued by Erickson and Gallino as they see fit when
they need help. Erickson and Gallino will be respondsible for each
sub-permitees actions.
We would also at that time present our plans for a study to determine
what effort the Cormorants are having on the fish population.
Sincerely,
[signature of Jim Erickson]
Jim Erickson
Rt. 1 Box 268
Nehalem, Or. 97131
[stamp of receipt dated April 25, 1989]
++++ start of p. *82 in SOO 6 (S6c.htm) | Contents | Index | References
**********************************************************************
[Verbatim transcription of Erickson's typed two-page letter; the third page of testimony was a copy of McAllister's [1988] newspaper article. A photocopy of the original typed letter is in the paper edition.]
**********************************************************************
[stamp by House Ag. & Natural Resources Committee, Bill No. HB 3185,
Exhibit H, 3 pages, Date: 4/13/89, Presented by Jim Erickson]
COMMITTEE OF H. B. 3185
This is not a lengthy report of bird problems all over the world but very
short to the point about the problems we face in our bays and estuarys in
Oregon with bird predation, especially the Cormorants.
Each spring the hatcheries release the salmon and steelhead smolts by the
thousands into the rivers either by truck or directly into the streams.
During the migration we observed these smolts held up in the bays and
estuarys for some reason and for varying lengths of time; From one to six
weeks before they leave for the ocean.
During this time the Cormorants can come into the bays and rivers and
completely wipe out these smolts balls with absolutely no interference
until 1988. During the hazing program in 1988 several things were found by
Federal Fish and Wildlife people and ourselves.
1. Cormorants are eating smolts at an alarming rate. These cormorants are
keyed in on the smolt migration and only come into the bays and rivers in
large numbers during the smolts migration during April, May and June.
2. Hazing works very well with the cormorants as it does with other
troublesome animals and birds with no noticable effect on other bird life
in the immeidate area. This can be done with the standard cracker shells
and screamer shells. Both these methods have proven to be both very
effective and cost efficient in other hazing programs and also worked the
the cormorants.
3. Hazing has already shown its value. More than 3x as many
steelhead jacks returned to the North Fork Nehalem River hatchery
this year than any previous year (with or without the weir) so we
have smolt survival, also if one sees large flocks
++++ start of p. *83 in SOO 6 (S6c.htm) | Contents | Index | References
of cormorants eating large amounts of smolts and we can prevent this from
happening with hazing. Hazing works. Seeing first hand the positive
effects of hazing on other species of animals and birds to protect a
resource it is hard to see why Oregon Deparment of Fish and Wildlife
haven't adopted a hazing program on all the rivers that plant steelhead and
salmon in the State ofOregon.
The conclusion is before the hazing program we saw thousands (or
hundredsdepends who you want to listen to) cormorants eating smolts. After
the hazing program was in operation we didn't see any cormorants eating any
smolts, so therefore to be very simple, hazing works without killing any
birds.
However we see a few problems with the number of permits issued and would
like the bill to say "at least 1 permit for Nehalem Bay and 2 permits for
Tillamook Bay with provisions for 2 "helpers" on each bay."
[signature of Jim Erickson]
Jim Erickson
Rt. 1 Box 268
Nehalem, Or. 97131
Phone; 368-5365
++++ start of p. *84 in SOO 6 (S6c.htm) | Contents | Index | References
***************************************************************************
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1005 Broadway NE, Salem, Oregon 97310.
++++ start of p. *87 in SOO 6 (S6c.htm) | Contents | Index |
Erickson, J. 1989d. [13 April 1989 written testimony to Oregon House
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