C. M. Neville

Evidence That Reduced Early Marine Growth is Associated with Lower Marine Survival of Coho Salmon

Abstract Coho salmon Oncorhynchus kisutch from the Strait of Georgia were used to test the hypothesis that slower growing fish in their first ocean year had lower survival over the late fall and winter than faster growing fish. The Strait of Georgia provided a suitable area for this study because it is a semi-enclosed rearing area for juvenile Pacific salmon that is distinct from the open marine rearing areas off the west coast. Coho salmon that survived the winter had significantly larger spacing between circuli on scales, indicating that brood year strength is related to growth in the first marine year. Other studies have shown that smaller fish of a cohort are less able to survive periods of energy deficit than larger fish. Thus, size-related mortality in the first marine fall and winter may be an important determinant of brood year strength of some coho salmon stocks and stocks of other species of Pacific salmon.

Hatchery and wild production of Pacific salmon in relation to large-scale, natural shifts in the productivity of the marine environment

Pacific salmon have been fished extensively for at least a century and artificial production of Pacific salmon has been a management strategy to improve production for almost as long. Hatchery production is considered important because it is commonly believed that the carrying capacity for salmon in the ocean has remained more or less constant and is underutilized as a consequence of limited production of smolts in fresh water. Since the mid-1960s, there has been an increase in hatchery production, partly as a response to a desire to increase catch and partly because of improved hatchery techniques. Since the late 1970s there has been a dramatic increase in the total Pacific salmon catch. The increases in catch are now known to result from a large-scale shift in the productivity of the sub-arctic Pacific and management and enhancement actions. Environmental indices changed about 1989-1990 and may indicate that the productive regime of the 1980s has ended. This would imply that under natural conditions Pacific salmon abundance would decline. There are no clear indications of what to expect in the new regime, but it is apparent that the massive production of artificially reared Pacific salmon would not be necessary in a less productive regime. Of concern is the impact that the large numbers of artificially reared salmon will have on wild salmon stock levels.

Replacement of Wild Coho Salmon by Hatchery-Reared Coho Salmon in the Strait of Georgia over the past Three Decades

Abstract The percentage of hatchery-reared coho salmon Oncorhynchus kisutch in the Strait of Georgia, British Columbia, increased from nearly 0% in the early 1970s to more than 70% by 2001. These estimates were derived from fin clip and coded wire tag data collected from commercial and sport fisheries, research surveys conducted in the summer and fall of 1997 to 2000, and examination of the microstructure of otoliths extracted from juvenile coho salmon collected during our marine surveys. The increasing trend may be related to the proportions of hatchery and wild smolts entering saltwater, fishing rates, and changes in the ecological processes regulating coho salmon production in the ocean. The consequence for management is that the abundance of wild spawning salmon (escapement) depends on hatchery as well as wild production. The consequence for policy makers is that future enhancement activities need to have clear policies for assessing the effects of hatchery fish on the population dynamics of wild fish...

Changes in the Population Ecology of Hatchery and Wild Coho Salmon in the Strait of Georgia

Abstract An analysis of the results of a 10-year study of the population ecology of juvenile hatchery and wild coho salmon Oncorhynchus kisutch in the Strait of Georgia produced new information about the interannual and interseasonal fluctuations in abundance and marine survival. A decline in the percentage of hatchery coho salmon was related to declines in hatchery fish abundance and marine survival; wild coho salmon abundance was more stable. The declining marine survival of hatchery coho salmon appeared to be related to a fixed average date of release from hatcheries and a possibility of earlier prey production. The relatively stable abundance of wild coho salmon may relate to a natural trend toward earlier ocean entry dates. Oscillations in hatchery coho salmon percentage and abundance were related to oscillations in abundance of juvenile pink salmon O. gorbuscha. The impact of oscillating density affected marine survival of hatchery coho salmon more than that of wild coho salmon. Marine survival and ...

The Synchronous Failure of Juvenile Pacific Salmon and Herring Production in the Strait of Georgia in 2007 and the Poor Return of Sockeye Salmon to the Fraser River in 2009

Abstract Trawl studies from 1998 to 2009 indicated that juvenile Pacific salmon Oncorhynchus spp. and Pacific herring Clupea pallasii represented 98 % of the fish in the surface waters of the Strait of Georgia during the day in the spring and early summer. Standardized catches of all juvenile Pacific salmon in the trawl surveys were lowest in 2007. Catches of young-of-the-year Pacific herring were also extremely low in 2007. Three years later, the 2007 year-class had the lowest recruitment to the fishery in recorded history. In 2007, juvenile coho salmon O. kisutch and Chinook salmon O. tshawytscha were small and had the lowest condition of the fish in all surveys as well as a high percentage of empty stomachs. The early marine survival of coho salmon in 2007 and the total survival in 2008 were exceptionally poor. Trawl catches of juvenile chum salmon O. keta in 2007 were the lowest of all surveys. Adult chum salmon from these juveniles that returned in 2010 had extremely poor survival. Juvenile sockeye salmon O. nerka that entered the Strait of Georgia in the spring of 2007 and returned to the Fraser River as adults in 2009 also had such exceptionally poor marine survival that a judicial inquiry was conducted to determine the causes. The synchronous poor growth, survival, or both of all of the major species in the surface waters of the Strait of Georgia in the spring of 2007 indicated that there was a common cause which we propose as poor food production. The causes of the high mortality likely represented a unique extreme in the variability of the factors that normally affect the survival of juvenile Pacific salmon and Pacific herring in the early marine period in the Strait of Georgia.

The importance of size as an isolating mechanism in lampreys

P. acuminatus: Brazil: Pernambuco: Recife (ZUEC 0372, 3 spec.). P. auratus: Trinidad (USNM 118240, 166629-166633, 166709-166710). P. brevirostris: Brazil: Paraiba: Alhandra (MZUSP 36784, holotype; MZUSP 36782-36783, 36785, paratypes). P. kautskyi: Brazil: Espirito Santo: Domingos Martins (El 7728, holotype); Bahia: SioJosi: Fazenda Unacau (MZUSP 63672-63673). P. luteolus: Brazil: Alagoas: Passo do Camaragibe (MN 10691); Bahia: Itabuna: CEPLAC (MN 10659-10682); Ilhius (MN 10683-10690); 15 km NW Porto Seguro (MZUSP 63153); Restinga de Alcobaga (MZUSP 20641-20642); Espirito Santo: Vit6ria (MZUSP 321); Guarapari (MZUSP 34042-34055); Vila Velha: Pontal da Fruta (ZUEC 5975-5985). P. tuberculosus: Brazil: Pernambuco: Caruaru (ZUEC not numbered); Sergipe: Santo Amaro das Brotas (MZUSP 49899-49901, 52769-52775, 52776-52789, 57005, 57007-57011, 57012-57028, 57037-57038).

Early Marine Survival of Coho Salmon in the Strait of Georgia Declines to Very Low Levels

Abstract The marine survival of juvenile coho salmon Oncorhynchus kisutch from the time they enter the Strait of Georgia in mid-May to the time of our trawl survey in mid-September declined from an average of about 15% in 1998 to approximately 1% in 2007. Early marine survival rates for juvenile coho salmon have been consistently low (<5%) since 2002, and the rate of decline in early marine survival was greater for hatchery fish than for wild fish. This suggests that hatchery coho salmon are perhaps less able to survive than wild fish in the current marine ecosystem. The steady decline in total marine survival for coho salmon over the past four decades coincided with a warming of the Strait of Georgia, where both sea surface and sea bottom temperatures have increased by approximately 1°C since 1970. Another factor that appears to have contributed to the decline in early marine survival since the late 1990s is an increase in the number of days with an average sustained wind strength greater than 25 km/h. The linkage between wind strength and marine survival requires further study, but wind strength is known to affect the timing and level of primary productivity. The processes that caused the declining marine survival remain to be identified and may include factors associated with disease originating in both freshwater and salt water, metabolic stress, competition, and predation. The data suggest that coho salmon brood year strength is now mostly determined during the first 4 months spent in the Strait of Georgia. If the current low levels of marine survival continue, management initiatives to protect wild coho salmon will be urgently required, and it will be timely to critically evaluate the hatchery programs and policies.

The Influence of Climate on the Stock and Recruitment of Pink and Sockeye Salmon from the Fraser River, British Columbia, Canada

The relationships between the spawning stock and the subsequent recruitment of pink salmon Oncorhynchus gorbuscha and sockeye salmon O. nerka from the Fraser River improve significantly when the data are separated by climate and ocean regimes. Our analyses show changes in these relationships as regimes shift, indicating that the trend in marine survival of pink and sockeye salmon changes on a decadal scale. In general, the climate and ocean regime from 1977 to 1988 was productive for pink and sockeye salmon. However, the regime in the 1990s was characterized by reduced productivity for both species. The occurrence of a natural shift in the trend of pink and sockeye salmon production on a decadal scale should be incorporated into the management of Pacific salmon stocks to ensure that annual catches, escapements, and planned stock abundances are consistent with the productivity of a particular regime.

Wild chinook salmon survive better than hatchery salmon in a period of poor production

The population dynamics of chinook salmon (Oncorhynchus tshawytscha) from the Cowichan River on Vancouver Island, British Columbia, Canada are used by the Pacific Salmon Commission as an index of the general state of chinook salmon coast wide. In recent years the production declined to very low levels despite the use of a hatchery that was intended to increase production by improving the number of smolts entering the ocean. In 2008, we carried out an extensive study of the early marine survival of the hatchery and wild juvenile chinook salmon. We found that both rearing types mostly remained within the Gulf Islands study area during the period when most of the marine mortality occurred for the hatchery fish. By mid September, approximately 1.3% of all hatchery fish survived, compared to 7.8%–31.5% for wild fish. This six to 24 times difference in survival could negate an estimated increased egg-to-smolt survival of about 13% that is theorized to result through the use of a hatchery. Estimates of the early marine survival are approximate, but sufficient to show a dramatic difference in the response of the two rearing types to the marine nursery area. If the declining trend in production continues for both rearing types, modifications to the hatchery program are needed to improve survival or an emphasis on improving the abundances of wild stocks is necessary, or both. The discovery that the juvenile Cowichan River chinook salmon remain within a relatively confined area of the Gulf Islands within the Strait of Georgia offers an excellent opportunity to research the mechanisms that cause the early marine mortalities and hopefully contribute to a management that improves the production.

Improvement of juvenile Pacific salmon production in a regional ecosystem after the 1998 climatic regime shift

Abstract Beginning in 2000, juvenile Pacific salmon Oncorhynchus spp. in the Strait of Georgia, British Columbia, fed more frequently, contained greater volumes of prey in their stomachs compared with the previous 3 years, and increased in size. Abundances in July also increased in 2000 and 2001. Marine survival increased, as indicated by the early marine survival of coho salmon O. kisutch in 2000 and 2001, which improved to more than twice the annual survival estimates for 1997–1999. Other indicators of improved marine survival included exceptional returns of pink salmon O. gorbuscha to the Fraser River in 2001 and sockeye salmon O. nerka in 2002. The change to a more productive regime for juvenile Pacific salmon was a lagged response to an abrupt change in climate in 1998, as shown by regional, basin-scale, and planetary indices.