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Guillem Chust Nerea Goikoetxea Leire Ibaibarriaga Yolanda Sagarminaga Igor Arregui Almudena Fontn Xabier Irigoien Haritz Arrizabalaga 《Fisheries Oceanography》2019,28(5):505-516
Marine species have exhibited trends in their geographic distribution and phenology in recent decades, and these changes are triggered by climate variability or anthropogenic pressures. Northeast Atlantic albacore has recently been identified to show changes of this nature, although the underlying causes are still uncertain. The aim of this work was to analyse the Northeast Atlantic albacore distribution shifts and phenological changes during the trophic migration that juveniles undertake from late spring to autumn and to identify potential causes of such variability. Specifically, time series of albacore catches of the Basque trolling fleet were studied and compared with trends derived from a null ecological niche model using very large number of catch observations (27,982). The results showed an earlier albacore migration of 2.3 days per decade during the period of 1981–2017, which was partly associated with the recent warming of the sea. The trend analysis of the catch distribution also detected a significant north‐westward trend in catch observations and a northward trend in species habitat. In contrast, both latitudinal trends were uncorrelated. This result suggests that interannual species distribution shifts are mainly related to factors other than oceanic‐climatic variability, such as fleet behaviour or prey changes. 相似文献
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M. G. PAWSON 《Aquaculture Research》1986,17(1):59-73
Abstract. Stock, catch and fishing effort statistics for a 12·5-ha lowland pul-and-lake trout fishery have been used to compute the ‘catchability’ of rainbow trout, Salmo gairdneri Richardson, during the fishing seasons 1980–1983. Seasonal trends in the fishes’ susceptibility to capture by fly-fishing are apparent but there was no indication that, in this fishery, newly stocked fish were more vulnerable than the longer-term residents. This consistency of recapture rates of rainbow trout, relative to the population available, is a function both of the fish's behaviour and that of the anglers themselves, and it is suggested that for management purposes the latter must be taken into account. In the fishery studied rainbow trout grew well at fish densities below 60 kg ha?1, but even with overall recapture levels exceeding 80% the yield of the fishery was less than the weight of fish stocked. The selection of strains of rainbow trout which satisfy the requirements of sport fisheries is discussed. 相似文献
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Ana M Queirós José Fernandes Lily Genevier Christopher P Lynam 《Fish and Fisheries》2018,19(4):613-621
Size‐based indicators are used worldwide in research that supports the management of commercially exploited wild fish populations, because of their responsiveness to fishing pressure. Observational and experimental data, however, have highlighted the deeply rooted links between fish size and environmental conditions that can drive additional, interannual changes in these indicators. Here, we have used biogeochemical and mechanistic niche modelling of commercially exploited demersal fish species to project time series to the end of the 21st century for one such indicator, the large fish indicator (LFI), under global CO2 emissions scenarios. Our modelling results, validated against survey data, suggest that the LFI's previously proposed policy target may be unachievable under future climate change. In turn, our results help to identify what may be achievable policy targets for demersal fish communities experiencing climate change. While fisheries modelling has grown as a science, climate change modelling is seldom used specifically to address policy aims. Studies such as this one can, however, enable a more sustainable exploitation of marine food resources under changes unmanageable by fisheries control. Indeed, such studies can be used to aid resilient policy target setting by taking into account climate‐driven effects on fish community size‐structure. 相似文献
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From small-scale habitat loopholes to decadal cycles: a habitat-based hypothesis explaining fluctuation in pelagic fish populations off Peru 总被引：22，自引：0，他引：22
Arnaud Bertrand Marceliano Segura Mariano Gutiérrez & Luis Vásquez 《Fish and Fisheries》2004,5(4):296-316
The Peru‐Humboldt Current system (HCS) supports the world's largest pelagic fisheries. Among the world's eastern boundary current systems, it is the most exposed to high climatic stress and is directly affected by El Niño and La Niña events. In this volatile ecosystem, fish have been led to develop adaptive strategies in space and time. In this paper, we attempt to understand the mechanisms underlying such strategies, focusing on the El Niño 1997–98 in Peru from which an extensive set of hydrographic, capture and acoustic survey data are available. An integrated analysis of the data is crucial, as each has substantial shortcomings individually; for example, both catch data and acoustic surveys may easily lead to wrong conclusions. Existing hypotheses on anchovy and sardine alternations lead us to a ‘habitat‐based’ synthetic hypothesis. Using our data, an integrated approach evaluated how fish responded to habitat variation, and determined the consequences in terms of fish‐population variability. Various factors occurring at a range of different spatio‐temporal scales were considered: interdecadal regime (warm ‘El Viejo’/cool ‘La Vieja’ decadal scale); strength and the duration of the El Niño Southern Oscillation event (interannual scale); population condition before the event (interannual scale); fishing pressure and other predation (annual scale); changes in reproductive behaviour (intra‐annual scale); presence of local upwelling (local scale). During El Niño 1997–98, anchovy was able to exploit a small‐scale temporal and spatial ‘loophole’ inside the general unfavourable conditions. Moreover, sardine did not do better than anchovy during this El Niño and was not able to take advantage of the ‘loophole’ opened by this short‐term event. Our results question the traditional view that El Niño is bad for anchovy and good for sardine. 相似文献
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Carrie J. Byron Andrew J. Pershing Jason D. Stockwell Huijie Xue John Kocik 《Fisheries Oceanography》2014,23(2):172-189
Understanding how oceanographic factors independently and interactively influence fish behavior, physiology, and survival is essential for predicting the impact of climate change on fish. Such predictions are especially challenging for highly migratory species such as salmon that experience a broad range of conditions. We applied a novel modeling approach that combines an individual‐based particle model with a bioenergetics model to evaluate the effects of oceanographic variability on migration of post‐smolt Atlantic salmon (Salmo salar). Interannual variability in the surface current velocity and sea surface temperature differentially influenced post‐smolt salmon migration. The magnitude, duration, and direction of the currents relative to a fish's intended swimming direction had the strongest influence on migration. Changes in ocean circulation led to changes in currents at a regional scale that have a similar, relative effect across multiple populations during out‐migration. Results of this study suggest that the Nova Scotia Coastal Current has a strong influence on the migration pathways of migrating salmon through the Gulf of Maine. The influx of cool fresh water from the Arctic, observed in the early 1990s, changed the Nova Scotia Coastal Current and, as suggested by model results, could have dramatically influenced post‐smolt salmon migration success. There was a trade‐off between arriving at the destination quickly but at a small size and not arriving at the destination at all. Fish that took a long time to migrate had more opportunities to feed and encountered warmer summer waters, increasing their overall growth. 相似文献
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Seasonal potential fishing ground prediction of neon flying squid (Ommastrephes bartramii) in the western and central North Pacific 
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下载免费PDF全文 Irene D. Alabia Sei‐Ichi Saitoh Robinson Mugo Hiromichi Igarashi Yoichi Ishikawa Norihisa Usui Masafumi Kamachi Toshiyuki Awaji Masaki Seito 《Fisheries Oceanography》2015,24(2):190-203
We explored the seasonal potential fishing grounds of neon flying squid (Ommastrephes bartramii) in the western and central North Pacific using maximum entropy (MaxEnt) models fitted with squid fishery data as response and environmental factors from remotely sensed [sea surface temperature (SST), sea surface height (SSH), eddy kinetic energy (EKE), wind stress curl (WSC) and numerical model‐derived sea surface salinity (SSS)] covariates. The potential squid fishing grounds from January–February (winter) and June–July (summer) 2001–2004 were simulated separately and covered the near‐coast (winter) and offshore (summer) forage areas off the Kuroshio–Oyashio transition and subarctic frontal zones. The oceanographic conditions differed between regions and were regulated by the inherent seasonal variability and prevailing basin dynamics. The seasonal and spatial extents of potential squid fishing grounds were largely explained by SST (7–17°C in the winter and 11–18°C in the summer) and SSS (33.8–34.8 in the winter and 33.7–34.3 in the summer). These ocean properties are water mass tracers and define the boundaries of the North Pacific hydrographic provinces. Mesoscale variability in the upper ocean inferred from SSH and EKE were also influential to squid potential fishing grounds and are presumably linked to the augmented primary productivity from nutrient enhancement and entrainment of passive plankton. WSC, however, has the least model contribution to squid potential fishing habitat relative to the other environmental factors examined. Findings of this work underpin the importance of SST and SSS as robust predictors of the seasonal squid potential fishing grounds in the western and central North Pacific and highlight MaxEnt's potential for operational fishery application. 相似文献
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Pierre Petitgas Adriaan D. Rijnsdorp Mark Dickey‐Collas Georg H. Engelhard Myron A. Peck John K. Pinnegar Ken Drinkwater Martin Huret Richard D. M. Nash 《Fisheries Oceanography》2013,22(2):121-139
To anticipate the response of fish populations to climate change, we developed a framework that integrates requirements in all life stages to assess impacts across the entire life cycle. The framework was applied on plaice (Pleuronectes platessa) and Atlantic herring (Clupea harengus) in the North Sea, Atlantic cod (Gadus morhua) in the Norwegian/Barents Seas and European anchovy (Engraulis encrasicolus) in the Bay of Biscay. In each case study, we reviewed habitats required by each life stage, habitat availability, and connectivity between habitats. We then explored how these could be altered by climate change. We documented environmental processes impacting habitat availability and connectivity, providing an integrated view at the population level and in a spatial context of potential climate impacts. A key result was that climate‐driven changes in larval dispersion seem to be the major unknown. Our summary suggested that species with specific habitat requirements for spawning (herring) or nursery grounds (plaice) display bottlenecks in their life cycle. Among the species examined, anchovy could cope best with environmental variability. Plaice was considered to be least resilient to climate‐driven changes due to its strict connectivity between spawning and nursery grounds. For plaice in the North Sea, habitat availability was expected to reduce with climate change. For North Sea herring, Norwegian cod and Biscay anchovy, climate‐driven changes were expected to have contrasting impacts depending on the life stage. Our review highlights the need to integrate physiological and behavioural processes across the life cycle to project the response of specific populations to climate change. 相似文献
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气候变化对海洋渔业资源的影响 总被引：5，自引：1，他引：4
气候变化问题是近年来国际社会关注的热点,海洋是气候系统储存能量的主要载体,气候变化给生活于其中的鱼类带来的影响不可忽视。气候的变化影响着各大洋低频气候变化模式以及海洋环境要素的变化,这些变化通过对鱼类个体的直接作用或生态系统食物链传递的间接作用影响海洋鱼类,包括鱼类的生理(生长、繁殖、洄游)、物候、资源量以及分布等,并形成了对海洋生态系统的影响,最终影响人类对渔业资源的管理。本文通过收集国内外相关文献,侧重从海洋鱼类资源量、分布变化以及海洋生态系统和渔业资源管理4个方面,综述了气候变化对渔业资源产生的影响,为应对气候变化、实现对渔业资源开发的可持续发展研究提供基础。 相似文献
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R. Eckmann 《Ecology of Freshwater Fish》1995,4(2):62-69
Fish species richness was assessed by electrofishing and gillnetting in 16 lakes of the northeastern lowland in Germany (the Schorfheide biosphere reserve). The lakes range from 0.03 to 10.55 km2 and support between 5 and 14 fish species. Species richness is significantly correlated with lake area in an exponential and a power model. Richness is also correlated with shoreline development and total dissolved solids. This supports the hypothesis that larger areas contain more species within a taxonomic group due to increased habitat diversity. The slope of the species-area curve is low compared with most other studies of fish species richness in lakes, and the intercept value is high. This is interpreted as the result of high habitat and food diversity, lack of stress from abiotic factors, and the small regional species pool from which these lakes can be colonized. Two species inventories, one from the beginning of this century and one from the 1950s, are available for comparison. Average species richness did not change during the last decades. Species turnover rates were not related to the degree of anthropogenic eutrophication or to the intensity of fishery exploitation in these lakes. On the species level, however, one effect of accelerated eutrophication is apparent, the disappearance of 4 bottom-living species from one to 6 of the study lakes. 相似文献
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Effects of climate on temporal variation in the abundance and distribution of the demersal fish assemblage in the Tsushima Warm Current region of the Japan Sea 下载免费PDF全文
下载免费PDF全文 In the present study, we examined the effects of climate on temporal variation in the abundance and geographical distribution of demersal fishes at both interannual and decadal scales in the Tsushima Warm Current region of the Japan Sea using single‐trawler fishery data (1972–2002). This single‐trawler fishery targeted multiple species with different geographical affinities and life history traits. Thus, these data were suitable for examining the biological mechanisms that underlie how species respond to climate variability. Our results indicate that the distributional changes of species in response to decadal climate variability are best explained by asymptotic length, which indicates that warming has greater negative effects on larger fishes in the Japan Sea. However, none of the variables examined (including geographical affinity, asymptotic length and age at maturation) could explain the shift in abundance at interannual or decadal scales. It should be noted that life history traits and geographical affinities only provide partial explanations of the responses of species to environmental variability, thereby suggesting that other factors, such as interactions among species, may be involved in mediating species responses. 相似文献
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Sarah Ann Thompson Marisol García‐Reyes William J. Sydeman Mayumi L. Arimitsu Scott A. Hatch John F. Piatt 《Fisheries Oceanography》2019,28(6):658-671
Climatic drivers of the size and body condition of forage fish in the North Pacific are poorly known. We hypothesized that length and condition of forage fish in the Gulf of Alaska (GoA) vary in relation to ocean temperature on multiple scales. To test this hypothesis, we analyzed morphometric data for capelin (Mallotus catervarius) and Pacific sand lance (PSL; Ammodytes personatus) sampled by a seabird (Cerorhinca monocerata) in two regions of the GoA, 1993–2016. Based on previous studies, we predicted that capelin length and body condition (Fulton's K) would be negatively related to the Pacific Decadal Oscillation (PDO) and sea surface temperature (SST), whereas PSL length and condition would be positively related. Interannual variation in length and body condition was evaluated relative to seasonal values of ocean climate using regression. Forage fish length and condition varied interannually, between sampling regions, and were dependent on the size/age class of the fish sampled. As predicted, length and body condition of capelin (mostly age 1+) were negatively related to the PDO and SST. Relationships with ocean climate for PSL varied by size/age class: positive for putative age‐0 fish and negative for putative age‐1+ fish. We conclude that our hypothesis was supported for capelin and partially supported for PSL. This study demonstrates that ocean climate determines key morphometric characteristics of forage fish that may relate to interannual variation in the energetic value of prey, and provides an example of how seabirds can be used to obtain specimens for evaluations of potential prey quality. 相似文献
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Does upwelling intensity determine larval fish habitats in upwelling ecosystems? The case of Senegal and Mauritania 下载免费PDF全文
下载免费PDF全文 Maik Tiedemann Heino O. Fock Patrice Brehmer Julian Döring Christian Möllmann 《Fisheries Oceanography》2017,26(6):655-667
European sardine (Sardina pilchardus) and round sardinella (Sardinella aurita) comprise two‐thirds of total landings of small pelagic fishes in the Canary Current Eastern Boundary Ecosystem (CCEBE). Their spawning habitat is the continental shelf where upwelling is responsible for high productivity. While upwelling intensity is predicted to change through ocean warming, the effects of upwelling intensity on larval fish habitat expansion is not well understood. Larval habitat characteristics of both species were investigated during different upwelling intensity regimes. Three surveys were carried out to sample fish larvae during cold (permanent upwelling) and warm (low upwelling) seasons along the southern coastal upwelling area of the CCEBE (13°–22.5°N). Sardina pilchardus larvae were observed in areas of strong upwelling during both seasons. Larval habitat expansion was restricted from 22.5°N to 17.5°N during cold seasons and to 22.5°N during the warm season. Sardinella aurita larvae were observed from 13°N to 15°N during cold seasons and 16–21°N in the warm season under low upwelling conditions. Generalized additive models predicted upwelling intensity driven larval fish abundance patterns. Observations and modeling revealed species‐specific spawning times and locations, that resulted in a niche partitioning allowing species' co‐existence. Alterations in upwelling intensity may have drastic effects on the spawning behavior, larval survival, and probably recruitment success of a species. The results enable insights into the spawning behavior of major small pelagic fish species in the CCEBE. Understanding biological responses to physical variability are essential in managing marine resources under changing climate conditions. 相似文献
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Abstract Temporal variation in production of the Chrysophrys auratus (Forster) fishery of Northern Spencer Gulf, South Australia, between 1984 and 2009 was investigated using commercial fishery statistics and estimates of age and size structures from market sampling. Fishery production was divisible into two periods, i.e. from 1984 to early 2000s and the middle to late 2000s. During the former, cycles in production were relatable to variable fishable biomass. Age structures that displayed considerable differences in age class strength reflected interannual variation in juvenile recruitment, which resulted in high variability in the strength of year classes entering the fishery. Periodic strong year classes were the major influence on fishable biomass as they passed through the population over numerous years. For the latter period, fishery statistics were conflicting as catches and effort were relatively low, whilst the estimates of catch per unit effort (CPUE) were consistently high. These statistics reflect a considerable change to the structure of the fishery that involved a reduction in number of fishers and fishing effort. The fishery statistics may indicate hyperstability, with CPUE estimates remaining high despite declining biomass because of the aggregative behaviour of the fish and the efficiency of remaining fishers. 相似文献
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Emily Fobert Grzegorz Zięba Lorenzo Vilizzi Michael J. Godard Michael G. Fox Saulius Stakėnas Gordon H. Copp 《Ecology of Freshwater Fish》2013,22(1):106-116
Predictions of future climate change include shifts in patterns of precipitation, evapotranspiration and water run‐off, resulting in increased periods of drought as well as variability and intensity of rainfall events. In the United Kingdom, the non‐native North American sunfish, pumpkinseed Lepomis gibbosus (L.), is expected to benefit from these changes. We examine how hydrological variability induced by predicted changes in climate will affect the dispersal and spread of pumpkinseed in England by: (i) determining the relationship between discharge regime and pumpkinseed propagule pressure; (ii) examining a newly‐established pumpkinseed population following a flood event in 2007; and (iii) comparing the growth and life‐history traits of this new population with fish collected from the source population to demonstrate how the pumpkinseed's life‐history plasticity contributes to its success as a coloniser. Using Bayesian modelling, we determined that the number of pumpkinseed escapees is likely to increase with increasing discharge. The newly‐established pumpkinseed population showed fast juvenile growth, early age at maturity and small size at maturity. These traits differed significantly from the source population, specifically total length (TL) means at ages 1 and 2 were significantly greater in the new population, whereas TL at age 4 was significantly greater in the source population, and a significantly higher proportion of mature females were found at smaller size classes in the newly established pumpkinseed population. This study demonstrates the potential link between hydrological variability (current and future) and the dispersal of non‐native pumpkinseed, leading to the establishment of new populations. 相似文献
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Undulatory swimming is employed by many fish for routine swimming and extended sprints. In this biomechanical review, we address two questions: (i) how the fish's axial muscles power swimming; and (ii) how the fish's body and fins generate thrust. Fish have adapted the morphology of their axial musculature for high power output and efficiency. All but the superficial muscle fibres are arranged along curved trajectories, and the myomeres form nested cones. Two conflicting performance goals shape the fibre trajectories of the axial muscles. Maximum power output requires that all fibres contract uniformly. In a bending fish, uniform contraction in a single myomere can be ensured by curved fibre trajectories. However, uniform strain is only desirable if all muscle fibres have the same contractile properties. The fish needs several muscle‐fibre types that generate maximum power at different contraction speeds to ensure effective muscle power generation across a range of swimming speeds. Consequently, these different muscle‐fibre types are better served by non‐uniform contractions. High power output at a range of swimming speeds requires that muscle fibres with the same contractile properties contract uniformly. The ensuing helical fibre trajectories require cone‐shaped myomeres to reduce wasteful internal deformation of the entire muscle when it contracts. It can be shown that the cone‐shaped myomeres of fish can be explained by two design criteria: uniform contraction (uniform strain hypothesis) and minimal internal deformation (mechanical stability hypothesis). So far, only the latter hypothesis has found strong support. The contracting muscle causes the fish body to undulate. These body undulations interact with the surrounding water to generate thrust. The resulting flow behind the swimming fish forms vortex rings, whose arrangement reflects the fish's swimming performance. Anguilliform swimmers shed individual vortex rings during steady swimming. Carangiform swimmers shed a connected chain of vortex rings. The currently available sections through the total flow fields are often not an honest representation of the total momentum in the water – the wake of carangiform swimmers shows a net backward momentum without the fish accelerating – suggesting that our current picture of the generated flow is incomplete. To accelerate, undulatory swimmers decrease the angle of the vortex rings with the mean path of motion, which is consistent with an increased rate of backward momentum transfer. Carangiform swimmers also enlarge their vortex rings to accelerate and to swim at a higher speed, while eel, which are anguilliform swimmers, shed stronger vortex rings. 相似文献
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Robert J. Lennox Henrik H. Berntsen Åse Helen Garseth Scott G. Hinch Kjetil Hindar Ola Ugedal Kjell R. Utne Knut Wiik Vollset Frederick G. Whoriskey Eva B. Thorstad 《Fish and Fisheries》2023,24(5):759-776
While populations of other migratory salmonids suffer in the Anthropocene, pink salmon (Oncorhynchus gorbusca Salmonidae) are thriving, and their distribution is expanding both within their natural range and in the Atlantic and Arctic following introduction of the species to the White Sea in the 1950s. Pink salmon are now rapidly spreading in Europe and even across the ocean to North America. Large numbers of pink salmon breed in Norwegian rivers and small numbers of individuals have been captured throughout the North Atlantic since 2017. Although little is known about the biology and ecology of the pink salmon in its novel distribution, the impacts of the species' introduction are potentially highly significant for native species and watershed productivity. Contrasts between pink salmon in the native and extended ranges will be key to navigating management strategies for Atlantic nations where the pink salmon is entrenching itself among the fish fauna, posing potential threats to native fish communities. One key conclusion of this paper is that the species' heritable traits are rapidly selected and drive local adaptation and evolution. Within the Atlantic region, this may facilitate further establishment and spread. The invasion of pink salmon in the Atlantic basin is ultimately a massive ecological experiment and one of the first examples of a major faunal change in the North Atlantic Ocean that is already undergoing rapid changes due to other anthropogenic stressors. New research is urgently needed to understand the role and potential future impacts of pink salmon in Atlantic ecosystems. 相似文献
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KO FUJIOKA ALISTAIR J. HOBDAY RYO KAWABE KAZUSHI MIYASHITA YOSHIMI TAKAO OSAMU SAKAI TOMOYUKI ITOH 《Fisheries Oceanography》2012,21(4):269-280
The arrival of the warm tropical Leeuwin Current (LC) into southern Western Australia (SWA) may influence the movement timing and foraging habitat of juvenile southern bluefin tuna (SBT). Seasonal and interannual changes in the strength of the LC lead to thermal differences and potential changes in food availability between tropical and temperate waters in SWA. This phenomenon could influence the habitat utilization of SBT in these summer grounds. Movement characteristics determined from SBT tagged with acoustic transmitters (N = 244) using cross‐shelf lines of automated receivers for three summer‐autumn seasons (2004/2005, 2005/2006, 2006/2007) in SWA revealed interannual variability. Each year, the eastward movements of tagged fish increased as temperatures increased, and fish left the region when temperatures exceeded 20.0°C, a temperature indicative of the leading edge of the LC in SWA waters. Interannual fluctuations in the timing of movements were detected. When the LC was narrow and restricted to the shelf edge in 2004/2005, the distribution of SBT in shelf waters did not change before or after LC intrusion. In contrast, long distance eastward movements frequently occurred when the LC intrusion was spread wide over the continental shelf in 2005/2006 and 2006/2007. This suggests that, off SWA, juvenile SBT move quickly out of local foraging habitats defined by cool sub‐tropical temperate waters ahead of the tropical LC intrusion, despite these waters not being physiologically limiting. These results suggest that the behavioural response of SBT may be related to changes in prey availability as a result of changes in oceanographic conditions. 相似文献
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SAYRE HODGSON THOMAS P. QUINN RAY HILBORN ROBERT C. FRANCIS DONALD E. ROGERS 《Fisheries Oceanography》2006,15(1):1-24
Interannual variation in the timing of the return migration to fresh water of adult sockeye salmon, Oncorhynchus nerka, from 46 populations throughout the species North American range was examined in a broad analysis of how timing patterns are affected by marine and freshwater conditions. Migration timing data (measured at various points along the migration, including just prior to freshwater entry, just after freshwater entry, and near the spawning grounds) were examined for correlations with sea‐surface temperatures (SST) prior to migration and to freshwater temperatures and flows during migration. Following a spring–summer period with warm SST, populations from southwestern Alaska tended to return early, Fraser River populations returned late, and populations from other regions showed no consistent patterns. Similarities between interannual timing of both nearby and distant populations indicated the presence of common or coincidental influences on timing. When riverine conditions related to timing, high flows and low temperatures were associated with late migrations, low flows and high temperatures were associated with early migrations. However, even counting stations at upriver locations showed correlations with SST. Notwithstanding some inconsistencies among the many populations examined and the indirect nature of the inferences, the results supported the hypotheses that (i) interannual variations in salmon distributions at sea reflect temperature conditions, and (ii) the date when salmon initiate homeward migration is a population‐specific trait, largely unaffected by the fish's location at sea. 相似文献