Habitat preferences of selected demersal fish species in the Bay of Biscay and Celtic Sea, North-East Atlantic

According to the Ideal Free Distribution theory, individual fish are distributed where environmental conditions are optimal, and the occupied area may vary with population abundance. Thus, observed distributions are a combination of habitat suitability and density-dependent effects. Data from an annual bottom trawl survey taking place in autumn were used to assess associations between the distributions of eight demersal fish species, separately for juveniles and adults, and habitat characteristics (depth, temperature and salinity) in the Bay of Biscay and Celtic Sea. Cumulative distribution functions were used to describe the general frequency distributions of environmental variables and their relationships with fish density. During the period 1992–2006, observed bottom temperatures fluctuated with no time trend (ΔT = 8°C in the first 80 m) and population abundances varied significantly. Juvenile hake, poor cod, blue whiting, adult red gurnard, adult megrim, and lesser-spotted dogfish were found to be significantly associated with specific depth ranges. Associations with bottom temperature and salinity were weaker. For some species, preferred environmental conditions changed over time, independently of variations in environmental conditions. In general, most species seemed to be able to cope with the experienced range of conditions. Habitat associations were not influenced by abundance variations. Fluctuating abundances had an impact on spatial occupation only for red gurnard adults, lesser-spotted dogfish and blue whiting juveniles, independent of absolute densities.     

Impacts of climate change on the complex life cycles of fish

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.     

Evaluating spatio‐temporal variability in the habitat quality of Atlantic cod (Gadus morhua) in the Gulf of Maine

Reduced abundance and contracted spatial distribution of Atlantic cod, Gadus morhua, in the Gulf of Maine (GOM) may indicate large spatio‐temporal variation in their habitat quality. Season‐specific Habitat Suitability Index (HSI) models were developed to quantify such variation in the offshore GOM management area. Data used were non‐zero cod catch rates with calibrations from the Northeast Fisheries Science Center (NEFSC) spring and fall bottom trawl surveys over the period 1982–2013 and key physical environmental variables including depth, bottom temperature, bottom salinity and sediment types. Significant declines were found in the average HSI across the study area in the springs of early 2000s and 2010s. These low average HSI values coincide with reduced age‐1 recruitment of GOM cod stock after the mid‐1990s. Moreover, the western coastal areas of the GOM generally exhibited higher average HSI values than the eastern coastal areas, whereas the offshore areas always had the lowest average HSI. Relatively higher cod survey catch rates in the western GOM may imply positive influences of environmental controls on the distribution of GOM cod.     

Spatio‐temporal analyses of marine predator diets from data‐rich and data‐limited systems

Accounting for variation in prey mortality and predator metabolic potential arising from spatial variation in consumption is an important task in ecology and resource management. However, there is no statistical method for processing stomach content data that accounts for fine‐scale spatio‐temporal structure while expanding individual stomach samples to population‐level estimates of predation. Therefore, we developed an approach that fits a spatio‐temporal model to both prey‐biomass‐per‐predator‐biomass data (i.e. the ratio of prey biomass in stomachs to predator weight) and predator biomass survey data, to predict “predator‐expanded‐stomach‐contents” (PESCs). PESC estimates can be used to visualize either the annual landscape of PESCs (spatio‐temporal variation), or can be aggregated across space to calculate annual variation in diet proportions (variation among prey items and among years). We demonstrated our approach in two contrasting scenarios: a data‐rich situation involving eastern Bering Sea (EBS) large‐size walleye pollock (Gadus chalcogrammus, Gadidae) for 1992–2015; and a data‐limited situation involving West Florida Shelf red grouper (Epinephelus morio, Epinephelidae) for 2011–2015. Large walleye pollock PESC was predicted to be higher in very warm years on the Middle Shelf of the EBS, where food is abundant. Red grouper PESC was variable in north‐western Florida waters, presumably due to spatio‐temporal variation in harmful algal bloom severity. Our approach can be employed to parameterize or validate diverse ecosystem models, and can serve to address many fundamental ecological questions, such as providing an improved understanding of how climate‐driven changes in spatial overlap between predator and prey distributions might influence predation pressure.     

Changes in spawning stock structure strengthen the link between climate and recruitment in a heavily fished cod (Gadus morhua) stock

Atlantic cod (Gadus morhua) is one of the commercially most important fish species in the North Atlantic and plays a central role in several ecosystems. Fishing pressure has been heavy over a prolonged period and the recent decades have shown dramatic decline in abundance of many stocks. The Arcto‐Norwegian (or North‐east Arctic) cod stock in the Barents Sea is now the largest stock of Atlantic cod. Recruitment to this stock has varied extensively during the last 60 yr. There is evidence for fluctuations in climate, particularly sea temperature, being a main cause for this variability, higher temperatures being favourable for survival throughout the critical early life stages. Our studies of time series present compelling evidence for a strengthening of the climate–cod recruitment link during the last decades. We suggest this is an effect of the age and length composition of the spawning stock having changed distinctly. The age of the average spawner has decreased by more than 3 yr from between 10 and 11 in the late 1940s to 7–8 in the 1990s, average length from just above 90 cm to around 80 cm. The number of age classes contributing to the spawning stock has also decreased, while the number of length groups present increased slightly. Significant decrease in age of spawners has frequently been described for other heavily fished stocks worldwide. We therefore find it likely that the proposed mechanism of increased influence of climate on recruitment through changes in the spawning stock age and size composition is of a general nature and might be found in other systems.     

Understanding what controls the spawning distribution of North Sea whiting (Merlangius merlangus) using a multi‐model approach

The processes that control the spatial distribution of North Sea whiting (Merlangius merlangus) spawning adults are investigated using a statistical multi‐model approach. Models of external and internal controls on the population, such as environmental conditions, spatial constraints, present or past spatial distribution, and demographic state of the population, are evaluated, compared and ranked to select those that are the best able to predict the observed distribution of spawning adults. Model selection is greatly influenced by the selection method, either based on data fitting or prediction, as well as by the threshold value used to stop the selection. Model selection based on prediction tends to select simpler models than selection based on data fitting. The hypotheses underlying the selected models are inferred to play a significant role in controlling North Sea whiting spatial distribution. The multi‐model inference approach developed in this study enables comparison of several theoretical concepts and hypotheses and the results provide important clues on the processes involved in the control of the spatial distribution of whiting. We conclude that whiting has a high spatial fidelity to spawning site which can be linked to either geographical attachment or year‐to‐year persistence of the spatial distribution of the population. Environmental factors – temperature and salinity – appear to influence the geographical extent of spawning whiting distribution, whereas local abundance levels are primarily controlled by internal factors, i.e., population size and spatial segregation between ages.     

Management of transboundary and straddling fish stocks in the Northeast Atlantic in view of climate‐induced shifts in spatial distribution

The introduction of 200 n.m. exclusive economic zones (EEZs) in the late 1970s required increased collaboration among neighbouring coastal states to manage transboundary and straddling fish stocks. The established agreements ranged from bilateral to multilateral, including high‐seas components, as appropriate. However, the 1982 United Nations Convention on the Law of the Sea does not specify how quotas of stocks crossing EEZs should be allocated, nor was it written for topical scenarios, such as climate change with poleward distribution shifts that differ across species. The productive Northeast Atlantic is a hot spot for such shifts, implying that scientific knowledge about zonal distribution is crucial in quota negotiations. This diverges from earlier, although still valid, agreements that were predominately based on political decisions or historical distribution of catches. The bilateral allocations for Barents Sea and North Sea cod remain robust after 40 years, but the management situation for widely distributed stocks, as Northeast Atlantic mackerel and Norwegian spring‐spawning herring, appears challenging, with no recent overall agreements. Contrarily, quotas of Northern hake are, so far, unilaterally set by the EU despite the stock's expansion beyond EU waters into the northern North Sea. Negotiations following the introduction of EEZs were undertaken at the end of the last cooler Atlantic Multidecadal Oscillation (AMO) period, that is, with stock distributions generally in a southerly mode. Hence, today's lack of management consensus for several widely distributed fish stocks typically relates to more northerly distributions attributed to the global anthropogenic signal accelerating the spatial effect of the current warmer AMO.     

Spatial and temporal patterns in summer ichthyoplankton assemblages on the eastern Bering Sea shelf 1996–2007

Larval and early juvenile fishes were sampled from the eastern Bering Sea (EBS) shelf from 2001 to 2005, and in 2007. Data from these collections were used to examine spatial and temporal patterns in species assemblage structure and abundance. The years 2001–2005 were unusual because the EBS water temperature was ‘warm’ compared with the long‐term mean temperature. In contrast, 2007 was a ‘cold’ year. The abundance of the five most numerous taxa at 12 stations common to all years sampled (1996–2005, 2007) were significantly different among years. Larval and early juvenile stage Theragra chalcogramma (walleye pollock), a commercially important gadid, were by far the most abundant fish in all years. Bottom depth alone best explained assemblage structure in most years, but in others, bottom depth and water column temperature combined and percent sea‐ice coverage were most important. Abundance of T. chalcogramma larvae increases with water column temperature until 5°C and then becomes level. Higher abundances of Gadus macrocephalus (Pacific cod) larvae occur in years with the greatest percent sea‐ice cover as indicated by GAM analysis. Larvae of Lepidopsetta polyxystra (northern rock sole) increase in abundance with increasing maximum wind speed, but decrease at a later date during the last winter storm. The data are consistent with the hypothesis that oceanographic conditions, specifically water temperature and sea‐ice coverage, affect the spatial and temporal pattern of larval abundances. In general, ichthyoplankton species assemblages can be important early indicators of environmental change in the Bering Sea and potentially other subarctic seas as well.     

Spatial distribution pattern and physical – biological interactions in the larval notothenioid fish assemblages from the Bransfield Strait and adjacent waters

The Bransfield Strait and adjacent waters represent one of the most important areas of larval retention off the Antarctic Peninsula. The species composition of larval fish assemblages has been described in detail in previous surveys carried out in the area, but the role of environmental parameters influencing the spatial distribution of early life stages was poorly known. By applying generalized additive models and multivariate analyses, we evaluated the role of environmental variables in shaping the small‐scale distribution of larval fish and investigated the spatial structure of the larval assemblage. It consisted of a few dominant notothenioid species, such as Champsocephalus gunnari, Lepidonotothen squamifrons, Lepidonotothen larseni, Pleuragramma antarctica and Trematomus scotti, and several other rarely caught species. Sea water temperature, salinity and sampling depth were the most important factors determining the spatial distribution of fish with different relative contributions, together explaining more than 80% of total deviance observed. Species richness was mostly affected by salinity, probably due to the narrow range of salinity preference by the species. Cluster analysis of abundance and presence data identified six and five distinct groups, respectively, each of them with substantial contributions of single or rarely two species. Differences in reproductive strategies of adult populations and spatial distribution of early life stages driven by different larval behaviour in response to environmental factors contribute to maintaining a well‐structured larval fish assemblage, ensuring spatial and food niche partitioning.     

Habitat associations of Atlantic herring in the Shetland area: influence of spatial scale and geographic segmentation

This study considers the habitat associations of a pelagic species with a range of biotic and abiotic factors at three different spatial scales. Generalized additive models (GAM) are used to analyse trends in the distributional abundance of Atlantic herring ( Clupea harengus ) in relation to thermocline and water depth, seabed roughness and hardness, sea surface salinity and temperature, zooplankton abundance and spatial location. Two geographical segments of the population, those east and west of the Shetland Islands (northern North Sea, ICES Div IVa), are examined. The differences in the ecological preferences of the species in these two distinct geographical areas are elucidated and the degree that these environmental relationships might be modulated by the change of support of the data is also considered. Part of the observed variability of the pre-spawning distribution of herring was explained by different parameters in these two regions. Notwithstanding this, key determinants of the species' spatial aggregation in both areas were zooplankton abundance and the nature of the seabed substrate. The relative importance of the variables examined did not change significantly at different spatial scales of the observation window. The diverse significance of various environmental factors on herring distribution was attributed mainly to the interaction of species' dynamics with the different characteristics of the ecosystem, east and west of the Shetland Islands. Results suggest that the current 2.5 nautical miles as elementary sampling distance unit (ESDU) is a reasonable sampling scheme that combines the need to reduce the data volume while maintaining spatial resolution to distinguish the species/environment relationships.     

Trophic role of Atlantic cod in the ecosystem

As the world's oceans continue to undergo drastic changes, understanding the role of key species therein will become increasingly important. To explore the role of Atlantic cod ( Gadus morhua Gadidae) in the ecosystem, we reviewed biological interactions between cod and its prey, predators and competitors within six ecosystems taken from a broad geographic range: three are cod-capelin ( Mallotus villosus Osmeridae) systems towards cod's northern Atlantic limit (Barents Sea, Iceland and Newfoundland–Labrador), two are more diverse systems towards the southern end of the range (North Sea and Georges Bank–Gulf of Maine), and one is a species-poor system with an unusual physical and biotic environment (Baltic Sea). We attempt a synthesis of the role of cod in these six ecosystems and speculate on how it might change in response to a variety of influences, particularly climate change, in a fashion that may apply to a wide range of species. We find cod prey, predators and competitors functionally similar in all six ecosystems. Conversely, we estimate different magnitudes for the role of cod in an ecosystem, with consequently different effects on cod, their prey and predator populations. Fishing has generally diminished the ecological role of cod. What remains unclear is how additional climate variability will alter cod stocks, and thus its role in the ecosystem.     

The growth of larval cod and haddock in the Irish Sea: a model with temperature,prey size and turbulence forcing

We applied a physiological individual‐based model for the foraging and growth of cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) larvae, using observed temperature and prey fields data from the Irish Sea, collected during the 2006 spawning season. We used the model to estimate larval growth and survival and explore the different productivities of the cod and haddock stocks encountered in the Irish Sea. The larvae of both species showed similar responses to changes in environmental conditions (temperature, wind, prey availability, daylight hours) and better survival was predicted in the western Irish Sea, covering the spawning ground for haddock and about half of that for cod. Larval growth was predicted to be mostly prey‐limited, but exploration of stock recruitment data suggests that other factors are important to ensure successful recruitment. We suggest that the presence of a cyclonic gyre in the western Irish Sea, influencing the retention and/or dispersal of larvae from their spawning grounds, and the increasing abundance of clupeids adding predatory pressure on the eggs and larvae; both may play a key role. These two processes deserve more attention if we want to understand the mechanisms behind the recruitment of cod and haddock in the Irish Sea. For the ecosystem‐based management approach, there is a need to achieve a greater understanding of the interactions between species on the scale a fish stock is managed, and to work toward integrated fisheries management in particular when considering the effects of advection from spawning grounds and prey–predator reversal on the recovery of depleted stocks.     

Coexisting invasive gobies reveal no evidence for temporal and trophic niche differentiation in the sublittoral habitat of Lake Erhai,China

Niche differentiation facilitates the coexistence of species within a community through avoidance of competition via mechanisms involving spatial, temporal and/or trophic dimensions. Where invasive species coexist in their non‐native range, niche differentiation could allow their persistence at higher levels of abundance. Here, we tested whether there was temporal and/or trophic niche differentiation between two congeneric invasive goby species (Rhinogobius cliffordpopei and Rhinogobius giurinus) in the sublittoral habitat of Lake Erhai (south‐west China) through quantifying their diel and seasonal rhythm of locomotion activities, feeding activities and diet composition. Both species displayed two similar diel peaks in activity and two main feeding periods (6:00–10:00 and 18:00–22:00), with rhythms of locomotion and feeding activity not differing significantly between the species in each season. Their diets had a high degree of overlap, being primarily composed of macrozooplankton, aquatic insects and shrimp larvae, with no diel changes across the seasons. Thus, in this habitat, there was no clear temporal or trophic niche differentiation between the invasive congeners, indicating their coexistence with high temporal and trophic overlap. In conjunction with data from the littoral and profundal habitats, the gobies revealed different strategies across the habitats (e.g. spatial segregation, trophic niche differentiation) that minimised their competitive interactions and promoted their coexistence. This suggests that the interactions of invasive fishes during the integration into native communities can be context dependent, varying according to factors including habitat and the availability of food resources.     

Changes in the spawning habitat of two small pelagic fish in the Northwestern Mediterranean

We investigated the effects of three sea surface oceanographic variables (temperature, salinity, and chlorophyll a) on the abundance of eggs and larvae of two summer‐spawning species in the NW Mediterranean Sea, the anchovy Engraulis encrasicolus and the round sardinella Sardinella aurita, based on data from ichthyoplankton surveys carried out in the 1980s, 2000s, and 2010s. The environmental data showed an increase in seawater temperature and salinity along time, coupled with a decrease in chlorophyll a (proxy for primary production). These long‐term directional changes in environmental conditions helped explain the important reduction observed in the abundance of eggs and larvae of anchovy, as well as shrinking of spawning habitat in this species. At the same time, the probability of occurrence of round sardinella has increased from practically zero in the 1980s to probabilities near 1 along the coastal area of the study region in the two decades of the 21st century. Given that the trends observed in the environmental variables along the three decades of study are expected to continue during the 21st century, as a consequence of climate change, the spawning habitat of anchovy is expected to continue decreasing, while round sardinella habitat can expand. Considering that anchovy is of high commercial importance in NW Mediterranean fisheries, while round sardinella has very low commercial interest, our results show that the viability of small pelagic fisheries in the area may be compromised.     

Links between the recruitment success of northern European hake (Merluccius merluccius L.) and a regime shift on the NE Atlantic continental shelf

The distribution of northern European hake (Merluccius merluccius L.) extends from the Bay of Biscay up to Norwegian waters. However, despite its wide geographical distribution, there have been few studies on fluctuations in the European hake populations. Marine ecosystem shifts have been investigated worldwide and their influence on trophic levels has been studied, from top predator fish populations down to planktonic prey species, but there is little information on the effect of atmosphere–ocean shifts on European hake. This work analyses hake recruitment success (recruits per adult biomass) in relation to environmental changes over the period 1978–2006 in order to determine whether the regime shift identified in several abiotic and biotic variables in the North Sea also affected the Northeast Atlantic shelf oceanography. Hake recruitment success as well as parameters such as the sea surface temperature, wind patterns and copepod abundance changed significantly at the end of the 1980s, demonstrating an ecological regime shift in the Northeast Atlantic. Despite the low reproductive biomass recorded during the last decades, hake recruitment success has been higher since the change in 1989/90. The higher productivity may have sustained the population despite the intense fishing pressure; copepod abundance, warmer water temperatures and moderate eastward transport were found to be beneficial. In conclusion, in 1988/89 the Northeast Atlantic environment shifted to a favourable regime for northern hake production. This study supports the hypothesis that the hydro‐climatic regime shift that affected the North Sea in the late 1980s may have influenced a wider region, such as the Northeast Atlantic.     

长江口及邻近海域春、夏季浮游动物优势种时空生态位分析

为探究长江口及邻近海域春、夏季浮游动物优势种时空生态位, 利用 2016—2018 年春季(5 月)和夏季(8 月) 长江口及邻近海域浮游动物及环境调查数据, 分析了该海域浮游动物优势种时空生态位特征, 并基于冗余分析 (RDA)对优势种与环境因子之间的关系进行分析。结果表明, 春季优势种以近岸低盐种占绝对优势, 夏季优势种以近岸低盐种和暖水种共存, 夏季优势种数目高于春季, 春季第一优势种虫肢歪水蚤(Tortanus vermiculus)优势度和平均拥挤度均高于夏季。在时间和空间生态位上, 真刺唇角水蚤(Labidocera euchaeta)、虫肢歪水蚤、长额刺糠虾 (Acanthomysis longirostris)和球型侧腕水母(Pleurobrachia globosa)均为广生态位种, 而中华哲水蚤(Sinocalanus sinensis)为窄生态位种。相似生态位种为了实现共存, 在时间或空间上发生生态位的分化。空间生态位重叠指数高的种对多具有捕食与被捕食关系。时间生态位上高等级重叠种对关系占比(50.0%)远高于空间生态位高等级重叠种对关系(18.2%)。物种环境排序图通过展示优势种分布与环境因子之间的关系, 揭示了优势种在生境中的生态位分化现象。本研究探明的浮游动物优势种的时空生态位分布特征可为研究其种间共存关系、环境适应性及水质环境变动提供依据。     

A spatially explicit, individual-based model to assess the role of estuarine nurseries in the early life history of North Sea herring, Clupea harengus

Herring (Clupea harengus) enter and remain within North Sea estuaries during well‐defined periods of their early life history. The costs and benefits of the migrations between offshore spawning grounds and upper, low‐salinity zones of estuarine nurseries are identified using a dynamic state‐variable model, in which the fitness of an individual is maximized by selecting the most profitable habitat. Spatio‐temporal gradients in temperature, turbidity, food availability and predation risk simulate the environment. We modeled predation as a function of temperature, the optical properties of the ambient water, the time allocation of feeding and the abundance of whiting (Merlangius merlangus). Growth and metabolic costs were assessed using a bioenergetic model. Model runs using real input data for the Scheldt estuary (Belgium, The Netherlands) and the southern North Sea show that estuarine residence results in fitter individuals through a considerable increase in survival probability of age‐0 fish. Young herring pay for their migration into safer estuarine water by foregoing growth opportunities at sea. We suggest that temperature and, in particular, the time lag between estuarine and seawater temperatures, acts as a basic cue for herring to navigate in the heterogeneous space between the offshore spawning grounds at sea and the oligohaline nursery zone in estuaries.     

Climate change projections of commercial fish distribution and suitable habitat around north western Europe

Under future climate change, modification of temperature and salinity are expected to result in distribution shifts of marine organisms, including commercial fish and shellfish. Changes are anticipated everywhere, including in the seas of many important fishing nations. Species turnover will in turn result in both opportunities and threats to fishing industries. To determine the impacts for northwest European shelf fisheries, we project changes for 49 commercially important fish and shellfish species using an ensemble of five ecological niche models and three different downscaled climate change projections. The habitat suitability and latitudinal shifts projected from the recent past (1997–2016) to two futures (2030–2050; 2050–2070) were calculated for waters around the United Kingdom. Of the species examined, around half were projected to have consistently more suitable habitat in the future, including European seabass (Dicentrarchus labrax, Moronidae), sardine (Sardina pilchardus, Alosidae) and anchovy (Engraulis encrasicolus, Engraulidae). Conversely, it is suggested that UK waters will become less suitable for species including Atlantic cod (Gadus morhua, Gadidae) and saithe (Pollachius virens, Gadidae). Our comprehensive approach using a number of models and climate change scenarios shows that while there are differences in the magnitude of change between models, and while some models perform better for certain species compared with others, overall, the general trends in habitat suitability and abundance are robust across models and climate scenarios. This emphasises the value in using more than one modelling technique with different climate scenarios (i.e., an ensemble approach) to capture the uncertainty or agreement around climate change projections.     

Biogeography of pelagic food webs in the North Pacific

The tufted puffin (Fratercula cirrhata) is a generalist seabird that breeds throughout the North Pacific and eats more than 75 different prey species. Using puffins as samplers, we characterized the geographic variability in pelagic food webs across the subarctic North Pacific from the composition of ~10,000 tufted puffin meals (~56,000 prey items) collected at 35 colonies in the Gulf of Alaska (GoA) and Aleutian Archipelago. Cluster analysis of diet species composition suggested three distinct forage fish communities: (i) in the northern GoA, multiple age‐classes of coastal and shelf residents such as capelin, sand lance and herring dominated the food web, (ii) in the western GoA to eastern Aleutians, the shelf community was dominated by transient age‐0 walleye pollock, and (iii) in the western Aleutians, shelf‐edge and mesopelagic forage species such as squid, lanternfish, and Atka mackerel were prevalent. Geographic patterns of abundance of capelin and sand lance in tufted puffin diets were corroborated by independent research fisheries and diets of piscivorous fish, indicating that puffin diets reflect the local abundance of forage species, not just selection of favored species. Generalized additive models showed that habitat characteristics predict, in a non‐linear fashion, forage species distribution and abundance across two large marine ecosystems. We conclude that major biogeographic patterns in forage fish distribution follow gradients in key habitat features, and puffin diets reflect those patterns.