Alex C. Wertheimer

Status of Pacific Salmon and Steelhead Escapements in Southeastern Alaska

Abstract We evaluated the status of Pacific salmon and steelhead (Oncorhynchus mykiss) in southeastern Alaska. Of 9,296 spawning aggregates identified in this region, some data were available for 4,009 (43%), and 928 (10%) had sufficient information to analyze for escapement trend. Of those analyzed, 333 (36%) were increasing, 556 (60%) were stable, 37 (4%) were declining, and 2 (< 1%) showed precipitous declines. We evaluated risk of extinction of spawning aggregates using criteria similar to surveys outside Alaska. We rated 918 (99%) at no or low risk, 8 (∼ 1%) at moderate risk, and 2 (< 1%) at high risk. No spawning aggregates were identified as extinct based on our evaluation of escapement data dating back to 1960. Prior to 1960, two spawning aggregates, one sockeye salmon (0. nerka) and one chum salmon (0. keta), were identified as extinct based on responses to a postal questionnaire. The Alaska Department of Fish and Game grouped spawning aggregates into management units for each species. Management...

Adult Production of Chinook Salmon Reared at Different Densities and Released as Two Smolt Sizes

Abstract Chinook salmon (Oncorhynchus tshawytscha) were reared at densities of 6.6–24.3 kg/ m3 and released as small (9.7–10.3 g) or large (28.2–31.8 g) smolts to determine the effects of fish size at release and rearing density on postrelease growth and adult return rate. Density did not affect survival during rearing, but mean weights for both size-classes were significantly lower at the highest rearing densities (P < 0.05). Density and size at release affected adult return rates, which were lower for fish reared at high densities for both size-classes. However, the increased number of smolts produced at higher densities compensated for the reduced return rates by yielding a higher number of returning adults per unit volume of rearing space. The estimated costs for each adult produced were US

Comment: A Review of the Hatchery Programs for Pink Salmon in Prince William Sound and Kodiak Island, Alaska

11.10–12.00 for small smolts and

Early male maturity in two stocks of chinook salmon (Oncorhynchus tshawytscha) transplanted to an experimental hatchery in southeastern Alaska

13.10–23.80 for large smolts. The lowest costs were projected at the second-highest density (18.6 kg/m3) for small smolts and at the highest density (20.3 kg/m3) for large smolts.

Marine Vertical Distribution of Juvenile Chinook and Coho Salmon in Southeastern Alaska

Recently, Hilborn and Eggers (2000) have asserted that hatcheries in Prince William Sound (PWS), Alaska, have caused a decline in the productivity of wild pink salmon Oncorhynchus gorbuscha in PWS and that hatchery fish to a large degree have replaced, not enhanced, pink salmon returns. Pink salmon catches in PWS are currently at historic highs, averaging 27 million fish per year over the past decade. Over 85% of the harvest is from a system of large hatcheries (Pinkerton 1994; McNair 2000). There is concern that hatchery production may have been deleterious to wild pink salmon in PWS, complicating management and the achievement of escapement goals and reducing productivity (e.g., Tarbox and Bendock 1996). Hilborn and Eggers estimate that more than 90% of the recent annual production would have been attained by wild stocks alone in the absence of hatchery production. We, however, find compelling evidence that hatchery fish have greatly increased the total pink salmon harvest in PWS and that Hilborn and Eggers’s estimates of wild stock productivity in the hypothetical absence of hatchery fish are not credible. While countervailing trends in the abundance of wild and hatchery pink salmon in PWS superficially appear to support Hilborn and Eggers’s arguments, careful consideration of the evidence indicates that the program has had substantial net benefits. We address three central points of the Hilborn and Eggers paper: (1) that retrospective analysis indicates that the proportional increases in pink salmon production in PWS have been similar to those in regions of Alaska without major hatcheries, on the basis of which Hilborn and Eggers conclude there is no evidence from between-region comparisons that the large increases in the catch in PWS were due to hatcheries; (2) that, because wild stock productivity is correlated negatively with the magnitude of fry releases from hatcheries, wild stock fish would have produced more than 90% of the current record runs in PWS in the absence of hatcheries; and (3) that wild stock escapements (i.e., the number of reproducing wild salmon) have declined due to deleterious interactions with salmon released from hatcheries. Proportionality Argument

Relationship of size at return with environmental variation, hatchery production, and productivity of wild pink salmon in Prince William Sound, Alaska: does size matter?

Progeny of 1976-brood chinook salmon (Oncorhynchus tshawytscha) from the Chickamin and Unuk rivers in southeastern Alaska were reared to the smolt stage in a hatchery 250 km northwest of their natal streams. As fingerlings, the fish were separated into eight groups to test the effect of stock, time of release, smolt size at release, and culture salinity on marine survival and rates of early male maturity (mature males returning earlier than the youngest mature females; i.e., ≤4 years in age). A total of 13 397 Chickamin River and 22 508 Unuk River smolts were tagged and released from the hatchery in 1978. From 1978 to 1982, 1373 fish from the Chickamin River and 1634 fish from the Unuk River stock were recovered in fisheries or as maturing fish returning to the release site. Age-5 chinook salmon of both sexes from the Chickamin River were larger than those from the Unuk River stock (P < 0.05), but age-6 fish of both stocks were similar in size, regardless of sex. Rates of early male maturity were 5.4–16.7% in the Chickamin River stock and 70.6–96.0% for the Unuk River stock, and stock was significant (P < 0.030) in determining early-male maturity. Smolt size at release, culture salinity, and time of release did not affect maturation age of males in either stock.

Hooking Mortality of Chinook Salmon Released by Commercial Trollers

Abstract Vertical distributions of chinook salmon Oncorhynchus tshawytscha of marine ages x.0, x.1, and x.2 and coho salmon O. kisutch of age x.0 are reported for the marine waters of southeastern Alaska. (The number or letter preceding the decimal point indicates number of winters spent in freshwater, that following the decimal point indicates winters spent in salt water.) Understanding vertical distribution of prerecruit salmon may be useful in minimizing fishery bycatch. Salmon were caught to a depth of 36.6 m from chartered commercial power trollers fishing small hooks and lures. Sampling occurred throughout inside waters of the Alexander Archipelago and adjacent coastal waters during September 1986 and in inside waters near Ketchikan during February, May, and September 1987. Vertical distribution of salmon differed significantly by species and age-group: in September, age-x.0 coho salmon (mean fork length, 28.4 cm) were caught shallower than age-x.0 chinook salmon (27.3 cm); age-x.1 (44.2 cm) and age...

Survival and Straying of Auke Creek, Alaska, Pink Salmon Marked with Coded Wire Tags and Thermally Induced Otolith Marks

Pink salmon (Oncorhynchus gorbuscha) returning to Prince William Sound (PWS), Alaska, have increased to historically high levels of abundance in recent years, but average body size at return has declined. We examined how body size at return of PWS pink salmon was related to 10 biophysical factors, including the scale of hatchery production. We also examined the effect of body size at return on productivity of wild pink salmon in PWS. For the 1975–1999 brood years, we found that an index of total abundance of pink salmon in the Gulf of Alaska and sea surface temperature during the year of return best explained the variation in pink salmon body size over time. Body size at return was significantly correlated with productivity of wild pink salmon. We used stepwise-regression to fit a generalized linear version of the Ricker spawner-recruit model to determine if body size would explain significant variation in wild-stock productivity in context with other environmental variation, including hatchery production. The results indicate that variability in wild-stock productivity is primarily driven by density-independent factors in the marine environment, but that body size of wild spawners also significantly affects productivity of wild PWS pink salmon. We conclude that the success of large-scale enhancement increasing the total run in PWS may have contributed to the decline in body size because of density-dependent growth in the Gulf of Alaska. We used a simulation model to estimate the impact of hatchery-induced changes in adult body size on wild-stock production in PWS. We estimated an annual wild-stock yield loss of 1.03 million pink salmon, less than 5% of the annual hatchery return of 24.2 million adult pink salmon for brood years 1990–1999.

Biophysical Factors Associated with the Marine Survival of Auke Creek, Alaska, Coho Salmon

Abstract Immediate and short-term (1–5-d) hooking mortality associated with the incidental catch of chinook salmon Oncorhynchus tshawytscha was assessed during periods when troll fishing for that species (only) was prohibited. Two chartered power trollers fished their normal complements of gear directed at coho salmon O. kisutch in Hawk Inlet, southeastern Alaska. Wound location, fork length, and lure type were the factors principally associated with mortality of incidentally caught chinook salmon. Severity of the hooking wound was also related to mortality. Maximum-likelihood estimates (with 95% confidence intervals in parentheses) of total mortality were 24.5% (20.1–29.0%) for sublegal-sized (<66 cm fork length) chinook salmon and 20.5% (9.0–31.9%) for legal-sized chinook salmon. The delayed-mortality rates were used to recalculate hooking mortality estimates from previous tagging experiments in which it was assumed that no delayed mortality occurred for certain locations and severities of wounds. The r...

Maturation success of pink salmon (Oncorhynchus gorbuscha) and coho salmon (O. kisutch) held under three salinity regimes

Abstract Pink salmon Oncorhynchus gorbuscha fry from Auke Creek, Alaska, were marked with coded wire tags (CWTs) and, in some cases, thermally induced otolith marks, to investigate the effects of the CWT process on survival and straying. Pink salmon from Gastineau Hatchery that had been thermally marked provided a point of comparison. Marked fish were also used to estimate the natal composition of fish in nearby streams and at Auke Creek and Gastineau Hatchery. The survival of fish with both CWTs and thermal marks was significantly lower than that of fish with thermal marks alone but not significantly different from that of fish with CWTs alone. No effect of CWTs on straying was detected. The estimated straying rates were 4.4% and 6.7% for early-run and late-run Auke Creek fish, respectively, and 6.9% for Gastineau Hatchery fish. The observed straying and run composition estimates indicated a large-scale interchange of adult pink salmon among local streams, which may promote rapid colonization and recover...