Modelling the oceanic habitats of two pelagic species using recreational fisheries data

Defining the oceanic habitats of migratory marine species is important for both single species and ecosystem‐based fisheries management, particularly when the distribution of these habitats vary temporally. This can be achieved using species distribution models that include physical environmental predictors. In the present study, species distribution models that describe the seasonal habitats of two pelagic fish (dolphinfish, Coryphaena hippurus and yellowtail kingfish, Seriola lalandi), are developed using 19 yr of presence‐only data from a recreational angler‐based catch‐and‐release fishing programme. A Poisson point process model within a generalized additive modelling framework was used to determine the species distributions off the east coast of Australia as a function of several oceanographic covariates. This modelling framework uses presence‐only data to determine the intensity of fish (fish km^?2), rather than a probability of fish presence. Sea surface temperature (SST), sea level anomaly, SST frontal index and eddy kinetic energy were significant environmental predictors for both dolphinfish and kingfish distributions. Models for both species indicate a greater fish intensity off the east Australian coast during summer and autumn in response to the regional oceanography, namely shelf incursions by the East Australian Current. This study provides a framework for using presence‐only recreational fisheries data to create species distribution models that can contribute to the future dynamic spatial management of pelagic fisheries.     

Tracking shifts in Atlantic mackerel (Scomber scombrus) larval habitat suitability on the Northeast U.S. Continental Shelf

Climate change has altered the oceanographic environment and subsequently the habitats of marine species. Fish and invertebrate populations’ responses to habitat include movement with latitude and depth to remain within their fundamental niches. The northwest Atlantic mackerel (Scomber scombrus) population has fluctuated over the last century due in part to changes in the environment. We used species distribution models to understand the influence of the physical (temperature) and biological (zooplankton) environment on mackerel larval abundance, and how such relations have determined larval habitat suitability in the Northeast U.S. Shelf. Atlantic mackerel larval presence and abundance correlated with sea temperature and copepod abundances, suggesting that larval survival may be sensitive to specific temperatures and zooplankton prey. Predicted abundances were spatially interpolated to estimate Atlantic mackerel larval suitable habitat. Metrics for habitat quality indicate that the Mid‐Atlantic Bight has become less suitable over time. Since the 1970s, the proportion of Northeast U.S. Shelf suitable habitat located in the Mid‐Atlantic Bight has decreased, as southern New England and the western Gulf of Maine regions have become more suitable. Habitat suitability within the Northeast U.S. Shelf has shifted northeast: from the Mid‐Atlantic Bight‐southern New England border towards the northeast portion of southern New England. While total Northeast U.S. Shelf habitat suitability has decreased since the 1970s, the decline in the time series trend was not statistically significant. Thus, while select ecoregions have decreased in habitat suitability, larval habitat does not appear to be the only contributor to decreases in the U.S. Atlantic mackerel contingent.     

Oceanographic drivers of petrale sole recruitment in the California Current Ecosystem

This paper investigates environmental drivers of U.S. West Coast petrale sole (Eopsetta jordani) recruitment as an initial step toward developing an environmental recruitment index that can inform the stock assessment in the absence of survey observations of age‐0 and age‐1 fish. First, a conceptual life history approach is used to generate life‐stage‐specific and spatio‐temporally specific mechanistic hypotheses regarding oceanographic variables that likely influence survival at each life stage. Seven life history stages are considered, from female spawner condition through benthic recruitment as observed in the Northwest Fisheries Science Center West Coast Groundfish Bottom Trawl Survey (age‐2 fish). The study area encompasses the region from 40 to 48°N in the California Current Ecosystem. Hypotheses are tested using output from a regional ocean reanalysis model outputs and model selection techniques. Four oceanographic variables explained 73% of the variation in recruitment not accounted for by estimates based exclusively on the spawning stock size. Recruitment deviations were (a) positively correlated with degree days during the female precondition period, (b) positively correlated with mixed‐layer depth during the egg stage, (c) negatively correlated with cross‐shelf transport during the larval stage, and (d) negatively correlated with cross‐shelf transport during the benthic juvenile stage. While multiple mechanisms likely affect petrale sole recruitment at different points during their life history, the strength of the relationship is promising for stock assessment and integrated ecosystem assessment applications.     

Capture and handling stress affects the endocrine and ovulatory response to exogenous hormone treatment in snapper, Pagrus auratus (Bloch & Schneider)

Sexually mature female hatchery‐reared snapper, Pagrus auratus (Bloch & Schneider) were captured from sea cages by handline and injected at first capture (control) or 24 h after capture, transport and subsequent confinement (delayed injection) with either saline, luteinizing hormone releasing hormone analogue, human chorionic gonadotropin, or 17α‐hydroxyprogesterone. Blood was sampled before hormone treatment and again after 168 h, and fish were checked daily for ovulation. Plasma levels of 17β‐estradiol (E2), testosterone (T), 17α, 20β dihydroxy‐4‐pregnen‐3‐one (17, 20βP) and cortisol were determined by radioimmunoassay. The ovulatory response was assessed from the proportion of fish ovulating, ovulation volume, egg quality and fertility. A delay in injection resulted in significantly lower plasma E2 and T levels in response to hormone treatment, smaller ovulation volumes, and poorer egg quality than in control fish. The results are consistent with the generally inhibitory effects of stress on reproduction in fish, and confirm the requirement to treat fish with hormones designed to induce ovulation, as soon as possible after capture and disturbance.     

Seasonal changes in otolith increment width trajectories and the effect of temperature on the daily growth rate of young sardines

We studied the otolith microstructure and growth of sardine, Sardina pilchardus, in the North Aegean Sea (eastern Mediterranean Sea), using samples of larvae and juveniles that had hatched in winter (November–January) and winter–spring (February–May), respectively. The juveniles had developed during an extended period coinciding with marked pelagic ecosystem changes (from winter, mixed conditions to summer, stratified waters). To examine the relationship between environmental changes and the observed variability in their otolith increment–width trajectories (width‐at‐age), we summarized the shape of trajectories with a four‐parameter set estimated from a growth model fit to each width trajectory. The individual parameter sets were then related to the potential oceanographic conditions that fish experienced during their development, derived from a hydrodynamic–biogeochemical model (POM‐ERSEM), implemented in the sampling area. Substantial seasonal effects were demonstrated on the otolith microstructure (platykurtic versus leptokurtic trajectories in winter‐mixed versus summer‐stratified conditions), which were related to the progressive sea surface warming. In a subsequent step, in order to study the effect of oceanographic conditions on larval and juvenile daily growth rates, a GAM (Generalized Additive Model) analysis of otolith increment widths was carried out, using model‐derived oceanographic parameters and taking into account the ‘inherent otolith growth’, expressed by the explanatory variables ‘previous increment width’ and ‘Age’. Results showed a strong and positive, linear effect of temperature on the growth rate of winter‐caught larvae, whereas in juveniles, which had developed within a wide range of temperatures, an optimum temperature for growth was observed at around 24°C.     

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.     

南海北部主要捕捞种类最适开捕规格研究

根据南海水产研究所使用elefan技术基于体长数据求得的南海北部50种主要捕捞种类的von Bertalanffy生长参数，以Beverton-Holt模型计算最适开捕年龄后用von Bertalanffy生长方程计算其相应开捕体长，再参考实际调查最小性成熟体长、临界体长、拐点体长和Froese-Binohlan经验公式计算的初次性成熟体长范围等数据确定最适开捕规格；部份分海区研究的种类先确定同一种类于各海区的最适开捕规格，再考虑不同海区的适用性确定其在南海北部的最适开捕规格。本文研究了南海北部50种主要捕捞种类的最适开捕规格，结果表明，所求得的最适开捕规格比原广东、广西、福建“水产资源繁殖保护实施细则暂行规定”的开捕规格都大；建议选择19种在以往的生产中和历次调查研究中出现频率较高、产量较高的主要捕捞种类作为南海北部实行开捕规格保护幼鱼幼虾措施的指标种，并提出开捕规格的随机抽样检查方法。     

Macroalgal meadow habitats support fish and fisheries in diverse tropical seascapes

Canopy‐forming macroalgae can construct extensive meadow habitats in tropical seascapes occupied by fishes that span a diversity of taxa, life‐history stages and ecological roles. Our synthesis assessed whether these tropical macroalgal habitats have unique fish assemblages, provide fish nurseries and support local fisheries. We also applied a meta‐analysis of independent surveys across 23 tropical reef locations in 11 countries to examine how macroalgal canopy condition is related to the abundance of macroalgal‐associated fishes. Over 627 fish species were documented in tropical macroalgal meadows, with 218 of these taxa exhibiting higher local abundance within this habitat (cf. nearby coral reef) during at least one life‐history stage. Major overlap (40%–43%) in local fish species richness among macroalgal and seagrass or coral reef habitats suggest macroalgal meadows may provide an important habitat refuge. Moreover, the prominence of juvenile fishes suggests macroalgal meadows facilitate the triphasic life cycle of many fishes occupying diverse tropical seascapes. Correlations between macroalgal canopy structure and juvenile abundance suggests macroalgal habitat condition can influence levels of replenishment in tropical fish populations, including the majority of macroalgal‐associated fishes that are targeted by commercial, subsistence or recreational fisheries. While many macroalgal‐associated fishery species are of minor commercial value, their local importance for food and livelihood security can be substantial (e.g. up to 60% of landings in Kenyan reef fisheries). Given that macroalgal canopy condition can vary substantially with sea temperature, there is a high likelihood that climate change will impact macroalgal‐associated fish and fisheries.     

Habitat differentiation between sei (Balaenoptera borealis) and Bryde's whales (B. brydei) in the western North Pacific

Two closely related baleen whale species, sei and Bryde's whales, in the western North Pacific were studied to identify differences in habitat use. Data were obtained from May to August 2004 and 2005. This study examined the relationship between oceanographic features derived from satellite data and the distribution of sei and Bryde's whales using basic statistics. We investigated oceanographic features including sea surface temperature (SST), sea surface chlorophyll a (Chl‐a), sea surface height anomalies (SSHAs), and depth of the habitat. These two whale species used habitats with different SST, Chl‐a, and SSHA ranges. The 0.25 mg m^?3 Chl‐a contour (similar to the definition of the Transition Zone Chlorophyll Front) was a good indicator that separated the habitats of sei and Bryde's whales. Then generalized linear models were used to model the probabilities that the whale species would be present in a habitat and to estimate their habitat distribution throughout the study area as a function of environmental variables. The potential habitats of the two species were clearly divided, and the boundary moved north with seasonal progression. The habitat partitioning results indicated that SST contributed to the patterns of habitat‐use and might reflect differences in prey species between the two whales. This study showed that the habitats of the sei and Bryde's whales were clearly divided and their potential habitat‐use changed seasonally.     

Diverse juvenile life‐history behaviours contribute to the spawning stock of an anadromous fish population

Habitat quality often varies substantially across space and time, producing a shifting mosaic of growth and mortality trade‐offs across watersheds. Traditional studies of juvenile habitat use have emphasised the evolution of single optimal strategies that maximise recruitment to adulthood and eventual fitness. However, linking the distribution of individual behaviours that contribute to recruitment at the population level has been elusive, particularly for highly fecund aquatic organisms. We examined juvenile habitat use within a population of sockeye salmon (Oncorhynchus nerka) that spawn in a watershed consisting of two interconnected lakes and a marine lagoon. Otolith microchemical analysis revealed that the productive headwater lake accounted for about half of juvenile growth for those individuals surviving to spawn in a single river in the upper watershed. However, 47% of adults had achieved more than half of their juvenile growth in the downstream less productive lake, and 3% of individuals migrated to the estuarine environment during their first summer and returned to freshwater to overwinter before migrating back to sea. These results describe a diversity of viable habitat‐use strategies by juvenile sockeye salmon that may buffer the population against poor conditions in any single rearing environment, reduce density‐dependent mortality and have implications for the designation of critical habitat for conservation purposes. A network of accessible alternative habitats providing trade‐offs in growth and survival may be important for long‐term viability of populations.     

Relative influence of static and dynamic features on black‐footed albatross (Phoebastria nigripes) habitat use in central California Sanctuaries

Effective conservation of highly mobile species requires an understanding of the factors that influence their habitat use patterns, locally and within a large‐scale oceanographic context. We characterized the seasonal (chick‐rearing, post‐breeding) and inter‐annual (2004–2008) distribution and abundance of black‐footed albatross (Phoebastria nigripes; BFAL) along the central California continental shelf/slope using standardized vessel‐based surveys. We used a hypothesis‐based information‐theoretic approach to quantify the relative influence of environmental conditions on BFAL occurrence and abundance by assessing their association with: (i) local static bathymetric features, (ii) local and regional dynamic oceanographic processes, and (iii) seasonal and inter‐annual basin‐wide variability. While the presence/absence models yielded stronger results than the abundance models, both revealed that static and dynamic features influence BFAL habitat use. Specifically, occurrence was greatest near the shelf‐break, particularly in months with strong upwelling. High BFAL densities were associated with Rittenburg Bank, especially during the chick‐rearing season, periods of positive North Pacific Gyre Oscillation index and large northern monthly upwelling, evidenced by cool, salty waters in the study area. BFAL aggregation intensity was greatest onshore of the shelf‐break (200 m isobath). Behavioral observations reinforced the notion that transiting BFAL are widely dispersed near the shelf‐break and concentrate in large flocks of birds sitting on the water farther onshore. These results underscore the need to consider oceanographic processes at multiple spatial scales when interpreting changes in BFAL dispersion within marine sanctuaries, and highlight the feasibility of implementing bathymetrically defined protected areas targeting predictable BFAL aggregations within these larger management jurisdictions.     

Predicting the current and future suitable habitat distributions of the anchovy (Engraulis ringens) using the Maxent model in the coastal areas off central‐northern Chile

An assessment of climate change impacts on the habitat suitability of fish species is an important tool to improve the understanding and decision‐making needed to reduce potential climate change effects based on the observed relationships of biological responses and environmental conditions. In this study, we use historical (2010–2015) environmental sea surface temperature (SST), upwelling index (UI), chlorophyll‐a (Chl‐a) and biological (i.e., anchovy adults acoustic presence) data (i.e., Maxent) to determine anchovy habitat suitability in the coastal areas off central‐northern (25°S–32°S) Chile. Using geographic information systems (GIS), the model was forced by changes in regionalized SST, UI and Chl‐a as projected by IPCC models under the RPC (i.e., RCP2.6, RCP4.5, RCP6.0 and RCP8.5) emissions scenarios for the simulation period 2015–2050. The model simulates, for all RCP scenarios, negative responses in anchovy presence, reflecting the predicted changes in environmental variables, dominated by a future positive (warming) change in SST and UI, and a decrease in chlorophyll‐a (i.e., phytoplankton biomass). The model predicts negative changes in habitat suitability in coastal areas from north of Taltal (25°S) to south of Caldera (27°45′S) and in Coquimbo littoral zone (29°–30°12′S). The habitat suitability models and climate change predictions identified in this study may provide a scientific basis for the development of management measures for anchovy fisheries in the coastal areas of the South American coast and other parts of the world.     

Contrasted optimal environmental windows for both sardinella species in Senegalese waters

We investigate Sardinella aurita and Sardinella maderensis recruitment success relative to the variability of oceanographic conditions in Senegalese waters using generalized additive models (GAM). Results show that recruitment of both species is marked by a strong intra‐annual (seasonal) variation with minimum and maximum in winter and summer, respectively. Their interannual variations are synchronous until 2006 (recruitment decreasing), while from 2007 there is no synchrony. The model developed shows that sardinella recruitment variability is closely related to the tested environmental variables in the study area. However, the key environmental variables influencing the recruitment success are different for both species: the Coastal Upwelling Index and the sea surface temperature for S. aurita and S. maderensis, respectively. We report that recruitment success of S. aurita and S. maderensis are associated with distinct ranges of sea surface temperature, upwelling intensity, wind‐induced turbulence, concentration of chlorophyll‐a and north Atlantic oscillation index. Considering food security and socio‐economic importance of both stocks, we recommend that consideration is given to the environmental variability in the small pelagic fish national management plans, particularly in the context of climate change.     

Effects of the gill monogenean Zeuxapta seriolae (Meserve, 1938) and treatment with hydrogen peroxide on pathophysiology of kingfish, Seriola lalandi Valenciennes, 1833

Infections by the gill fluke Zeuxapta seriolae are a serious concern for sea cage aquaculture of kingfish, Seriola lalandi. The present study aimed to determine the pathophysiological effects of a progressive infection with Z. seriolae and the effects of treatment with hydrogen peroxide. For the progression of infection study, infected fish were taken from a sea cage farm, treated to remove parasites and then infected by cohabitation with heavily infected fish. Samples were taken at 2-week intervals for 8 weeks. Infection intensity peaked at 4 weeks post-infection (mean intensity 565.9) and the number of mature worms (2 mm fixed length or larger) peaked at 6 weeks post-infection. Attachment of Z. seriolae appeared to cause little localized pathology; however, the occurrence of hyperplastic lamellae increased as the infection progressed. Haemoglobin concentrations were negatively correlated with Z. seriolae intensity and were lower than controls at 4 weeks (35.8% decrease) and 6 weeks (57.4% decrease) post-infection. Blood lactate concentration and plasma osmolality increased throughout the course of infection. For the effect of treatment experiment, groups of infected and non-infected fish were sampled either before or after treatment with hydrogen peroxide. Treated fish from both infected and uninfected groups had increased plasma lactate, osmolality and pH compared with pre-treatment groups. Treatment with hydrogen peroxide appeared to have acute effects on fish health but the magnitude (e.g. lactate, osmolality) and extent of the effects (e.g. haemoglobin) was much less than that caused by chronic infection with Z. seriolae.     

Alligator gar (Atractosteus spatula,Lacépède 1803) vitellogenin: purification,characterization and establishment of an enzyme‐linked immunosorbent assay

Alligator gar (Atractosteus spatula) is a non‐teleost bony fish distributed in North America. Gar populations have drastically declined as a consequence of habitat deterioration and the lack of regulation for their capture. Control of reproduction is critical for recovering their natural populations. The impossibility to distinguish genders and the determination of sexual maturity have hindered their successful reproduction. This research was aimed at developing an enzyme‐linked immunosorbent assay (ELISA) for the quantitative estimation of vitellogenin (VTG), a female‐specific protein. Plasmatic VTG from 17β‐estradiol (E2)‐induced juveniles and ovary vitellin from adult females were purified and characterized. Polyclonal antibodies against both proteins were produced to develop an ELISA. The immunoassay was validated by quality tests such as sensitivity, parallelism, recovery, reproducibility and specificity. Vitellogenin was determined in different tissues (plasma, mucus, liver and gills) of alligator gar. Vitellogenin and E2 concentrations in female breeders were found to be higher in November, before the spring spawning season. This approach represents a quick, reliable and non‐invasive practical alternative to distinguish genders and evaluate gonad maturation.     

Modelling Atlantic mackerel spawning habitat suitability and its future distribution in the north‐west Atlantic

We investigated the effect of environmental conditions on Atlantic mackerel spawning habitat in the southern Gulf of St. Lawrence (sGSL). Based on generalized additive models, we (i) modelled the optimal spawning habitat of mackerel in the sGSL using daily egg production (DEP) in June, (ii) predicted known and new potential present spawning habitats in the GSL and the north‐west Atlantic, and (iii) assessed how they respond to future climate change. Our findings showed that both mackerel presence–absence and given‐presence DEP were associated with sea surface temperature (10–16.5°C), salinity above 31 and depth < 120 m. Adding zooplankton showed a marked effect on the DEP given‐presence compared to the presence–absence. Predictions of spawning habitats under present (1999–2012) and future scenario (2066–2085) conditions were estimated from the presence–absence model without zooplankton, using physical conditions of the BNAM. Under present conditions, our model predicted well the main spawning habitat in the sGSL and other known secondary spawning habitats in the northern GSL (nGSL), the western and southern Newfoundland, and the north‐west Atlantic coast. Under future conditions, our study suggests that spawning habitats in the sGSL and the nGSL would expand. Our results, therefore, suggest that mackerel could benefit from a warmer GSL, minimizing the potential for a northward migration of the stock due to decreasing suitability of the sGSL as its main spawning ground, and a new but spatially limited potential habitat in Newfoundland coasts. These results can be used to inform stock management and develop adaptive management plans in the context of climate change.     

Quantifying the effects of wind, upwelling, curl, sea surface temperature and sea level height on growth and maturation of a California Chinook salmon (Oncorhynchus tshawytscha) population

We used retrospective scale growth chronologies and return size and age of female Chinook salmon (Oncorhynchus tshawytscha) from a northern California, USA, population collected over 22 run years and encompassing 18 complete cohorts to model the effects of oceanographic conditions on growth during ocean residence. Using path analyses and partial least squares regressive approaches, we related growth rate and maturation to seven environmental variables (sea level height, sea surface temperature, upwelling, curl, scalar wind, northerly pseudo‐wind stress and easterly pseudo‐wind stress). During the first year of life, growth was negatively related to summer sea surface temperature, curl and scalar winds, and was positively related to summer upwelling. During the second, third and fourth growth years growth rate was negatively related to sea level height and sea surface temperature, and was positively related to upwelling and curl. The age at maturation and the fork length at which three ocean‐winter fish returned were related to the environment experienced during the spring before the third winter at sea (the year prior return). Faster growth during the year before return led to earlier maturation and larger return size.     

Broad‐scale habitat classification variables predict maximum local abundance for native but not non‐native trout in New York streams

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不同气候模态下秘鲁外海茎柔鱼栖息地的季节性分布

茎柔鱼（Dosidicus gigas）为环境敏感型头足类,气候的多元变化促使茎柔鱼栖息地发生变动。本研究利用海表温度（SST）和海表面高度（SSHA）两个关键环境因子构建栖息地适宜性指数（HSI）模型,结合太平洋年代际涛动（PDO）指数,分析1950-2015年不同气候模态下秘鲁外海茎柔鱼栖息地的季节性分布规律。结果发现,PDO冷期茎柔鱼栖息地适宜性较高;而PDO暖期栖息地适宜性较低。相较于PDO冷期,PDO暖期下茎柔鱼适宜栖息地分布向东南移动。适宜栖息地的分布位置与适宜的SST和SSHA的重叠区域重合,表明两个关键环境因子与栖息地分布显著相关。此外,适宜栖息地指数距平值与PDO指数的年际变化呈显著负相关关系。春季茎柔鱼渔场栖息地适宜性高于冬季,且冬季适宜栖息地的分布相较春季偏东南方向。茎柔鱼渔场6-11月适宜的SST和最适宜的SST在经度和纬度上的分布存在显著差异,春季（9-11月）最适宜的SST分布逐月向西北方向移动;冬季（6-8月）最适宜的SST分布逐月向东南方向移动。推测不同气候模态下茎柔鱼栖息地季节性分布差异,可能是由于最适宜的SST显著的月间分布差异所致。研究表明,不同PDO时期下茎柔鱼栖息地适宜性具有显著季节性差异,其差异可由环境因子的月间变动来解释。     

Modelling the impacts of environmental variation on habitat suitability for Pacific saury in the Northwestern Pacific Ocean

We developed habitat suitability index (HSI) models for two size classes of Pacific saury Cololabis saira in the Northwestern Pacific Ocean. Environmental data, including sea surface temperature, sea surface height, salinity, and net primary production, and catch and effort data from Taiwanese distant‐water stick‐held dip net fisheries during the main fishing season (August–October) during 2002–2015 were used. Habitat preferences and suitable habitat area differed between size classes. The suitable habitat was located between 40–47.5°N and 145–165°E for large‐sized Pacific saury but encompassed a greater area (35–47°N and 140–165°E) for medium‐sized Pacific saury. Both size classes were affected by substantial interannual variation in the environmental variables, which in turn can be important in determining the potential fishing grounds. We found a significant negative relationship between the suitable habitat area and the Niño3.4 indices with a time‐lag of 6 months for the large‐sized (r = ?0.68) and medium‐sized (r = ?0.42) Pacific saury, respectively, as well as the total landings of Pacific saury by all fishing fleets (r = ?0.46). As remotely‐sensed environmental data become increasingly available, HSI models may prove useful for evaluation of possible changes in habitat suitability resulting from climate change or other environmental phenomena and in formulating scientific advice for management.