Distribution Of Hake Research Articles

Spatially varying effects of the California Undercurrent on Pacific hake distribution

In the California Current Ecosystem, the California Undercurrent (CU) is the predominate subsurface current that transports nutrient-rich water from southern California poleward. In this study, we used a large dataset of spatially explicit in situ observations of Pacific hake ( Merluccius productus) and the CU (36.5–48.3°N) to estimate relationships between northward undercurrent velocity and hake distribution and determine whether these relationships vary across space or life-history stage. We found that both hake occurrence and density had strong spatially complex relationships with the CU. In areas north of 44°N (central Oregon), the CU effect was spatially consistent and opposite for occurrence (negative) and density (positive), indicating that hake may aggregate in areas of high northward velocity in this region. In areas south of 44°N, the CU effect showed a cross-shelf gradient for both occurrence and density, indicating a more nearshore hake distribution when northward velocity is higher in this region. Together, our results suggest that future changes in the CU due to climate change are likely to impact hake differently in northern and southern areas.

Can Seasonal Forecasts of Ocean Conditions Aid Fishery Managers? Experiences from 10 Years of J-SCOPE

Multiple stressors co-occurring in coastal waters are of increasing concern to local fisheries. Many economically, culturally, or ecologically important species (e.g., oysters, crabs, pteropods) in the Pacific Northwest are already directly affected by ocean acidification (OA), warming, and hypoxia. Additional indirect economic impacts on the finfish industry are possible due to losses of prey species. Because of strong seasonal and interannual variations in ocean conditions, capability for predicting degrees of acidification and hypoxia, as well as relevant indices of impact for species of interest, could be of considerable benefit to managers. Over the past 10 years, we have developed a seasonal ocean prediction system, JISAO’s Seasonal Coastal Ocean Prediction of the Ecosystem (J-SCOPE), for the coastal waters of the Pacific Northwest. The goal has been to provide seasonal (six-month) predictions of ocean conditions that are testable and relevant to management decisions regarding fisheries, protected species, and ecosystem health. The results of this work include publicly available seasonal forecasts of OA variables, hypoxia, temperature, and ecological indicators that are tailored for decision-makers involved in federal, international, state, and tribal fisheries. We codesigned J-SCOPE model products with state and tribal managers, and now federal managers at the Pacific Fishery Management Council receive J-SCOPE forecasts of OA and hypoxia within their annual Ecosystem Status Reports. US and Canadian managers of Pacific hake (Merluccius productus) are now briefed on J-SCOPE-driven forecasts of hake distribution. Most recently, new ocean acidification indices specific to Dungeness crab (Metacarcinus magister) have been co-produced with state and tribal managers. In each of these cases, the team has also investigated the sources of skill in forecasting ocean conditions to assess applicability of the forecasts to the variables, depths, and seasons relevant to these high-value fisheries. Observations from NOAA’s Pacific Marine Environmental Laboratory and other regional partners have provided critical validation of model performance throughout the model development process. We offer a retrospective look at the first 10 years of forecasting to provide perspective on its successes and limitations, and the potential global applicability of seasonal forecasting to inform flexible management responses to rapidly changing climate and ocean conditions.

European hake (Merluccius merluccius, Linnaeus 1758) spillover analysis using VMS and landings data in a no-take zone in the northern Catalan coast (NW Mediterranean)

The analysis of fish spillover from marine protected areas (MPA) is often based on data collected after the implementation of protection. In the present study we used a methodology based on the combination of Vessel Monitoring System (VMS) and landings data before and after the establishment of protection for spillover analysis. We defined areas of similar size to the protected zone in order to compare them over time. In addition to the no-take zone effectiveness, using this methodology, we were also able to analyze the spatiotemporal behavior of the hake population. Our results on the hake distribution were consistent with those of previous studies. The juveniles were concentrated on the continental shelf (0 - 200 m), whereas the adults were found over the shelf and the slope (300 - 500 m). We found evidence suggesting a positive spillover effect for the juveniles on the continental shelf, enhancing its fishing yields. The analysis of longer time series on the performance of the protected area combined with field sampling inside the no-take zone would lead us to confirm effective spillover effect contributing to fisheries’ long-term sustainability in this zone.

The Seasonal Distribution of a Highly Commercial Fish Is Related to Ontogenetic Changes in Its Feeding Strategy

Improving the knowledge on the biology, ecology and distribution of marine resources exploited by fisheries is necessary to achieve population recovery and sustainable fisheries management. European hake (Merluccius merluccius) is one of the most important target species in the Mediterranean Sea and is largely overexploited by industrial fisheries. Here, we used two methodological approaches to further investigate the seasonal variation in the spatial distribution of European hake considering ontogenetic changes and trophic ecology in the western Mediterranean Sea. Our main aim was to explore if spatial changes in hake distribution were related to trophic behavior, in addition to key environmental factors. We employed a hierarchical Bayesian species distribution modeling approach (B-SDM), using spatial data from two oceanographic surveys conducted during winter and summer. We analyzed how the environmental variables, together with abundance and mean weight distribution of the main preys identified for European hake, affected the seasonal distribution of the species. Results revealed clear differences in the distribution of the European hake between seasons, which were indeed partially correlated to the distribution of their main preys, in addition to the environment. Stable isotope values and Bayesian isotopic mixing models (MixSIAR) revealed substantial seasonal and ontogenetic differences in trophic habits of European hake, partly matching the spatial distribution results. These findings could have implications for a future seasonal-based adaptive fisheries management, as local depletion of prey, or variation in size and condition may affect European hake presence in this area. Moreover, this study illustrates how the sequential application of methodologies provides a more holistic understanding of species seasonality, which is essential to understand the phenological processes of exploited species and their potential shifts due to environmental changes.

Environmentally Driven Seasonal Forecasts of Pacific Hake Distribution

Changing ecosystem conditions present a challenge for the monitoring and management of living marine resources, where decisions often require lead-times of weeks to months. Consistent improvement in the skill of regional ocean models to predict physical ocean states at seasonal time scales provides opportunities to forecast biological responses to changing ecosystem conditions that impact fishery management practices. In this study, we used 8-month lead-time predictions of temperature at 250 m depth from the J-SCOPE regional ocean model, along with stationary habitat conditions (e.g., distance to shelf break), to forecast Pacific hake (Merluccius productus) distribution in the northern California Current Ecosystem. Using retrospective skill assessments, we found strong agreement between hake distribution forecasts and historical observations. The top performing models (based on out-of-sample skill assessments using the area-under-the-curve (AUC) skill metric) were a generalized additive model (GAM) that included shelf-break distance (i.e., distance to the 200 m isobath) (AUC = 0.813) and a boosted regression tree (BRT) that included temperature at 250 m depth and shelf-break distance (AUC = 0.830). An ensemble forecast of the top performing GAM and BRT models only improved out-of-sample forecast skill slightly (AUC = 0.838) due to strongly correlated forecast errors between models (r = 0.88). Collectively, our results demonstrate that seasonal lead-time ocean predictions have predictive skill for important ecological processes in the northern California Current Ecosystem and can be used to provide early detection of impending distribution shifts of ecologically and economically important marine species.

Relationships between temperature and Pacific hake distribution vary across latitude and life-history stage

Environmental conditions can have spatially complex effects on the dynamics of marine fish stocks that change across life-history stages. Yet the potential for non-stationary environmental effects across multiple dimensions, e.g. space and ontogeny, are rarely considered. In this study, we examined the evidence for spatial and ontogenetic non-stationary temperature effects on Pacific hakeMerluccius productusbiomass along the west coast of North America. Specifically, we used Bayesian additive models to estimate the effects of temperature on Pacific hake biomass distribution and whether the effects change across space or life-history stage. We found latitudinal differences in the effects of temperature on mature Pacific hake distribution (i.e. age 3 and older); warmer than average subsurface temperatures were associated with higher biomass north of Vancouver Island, but lower biomass offshore of Washington and southern Vancouver Island. In contrast, immature Pacific hake distribution (i.e. age 2) was better explained by a nonlinear temperature effect; cooler than average temperatures were associated with higher biomass coastwide. Together, our results suggest that Pacific hake distribution is driven by interactions between age composition and environmental conditions and highlight the importance of accounting for varying environmental effects across multiple dimensions.

Towards a spatial integrated stock assessment model for European hake northern stock

European hake (Merluccius merluccius) is a key species in the management of several mixed fisheries in the north-east Atlantic where regional spatial management plans are being set up. The wide spatial distribution of hake and the lack of knowledge of some processes involved in its spatial dynamics could hamper the assessment and management of hake.To help understand the processes, we implemented a spatial version of the Stock Synthesis stock assessment model for northern hake, including available data on this stock and the associated fisheries. For the 1978–2012 time series, the model distinguished the Bay of Biscay, the Celtic Sea and a northern area aggregating the West of Scotland and the North Sea. The model considered an age-structured population for each age class and area, a seasonal migration, global recruitment allocated to areas and fishing fleets for each area. Parameters for stock and exploitation spatio-temporal dynamics were estimated by likelihood maximization for each quarter and area.The comparison of spatial and non spatial models goodness of fit showed they were close, although the fit to abundance indices slightly improved with the spatial model.Fishing mortalities, spawning stock biomasses and recruitments were slightly different from the current assessment model estimates, essentially at the beginning and the end of the time series. On average over the time series, fishing mortality estimates relative to the abundance were higher in the Bay of Biscay than elsewhere, spawning stock biomass estimates were higher in the Celtic Sea than elsewhere, and recruitment occurred mainly in the Bay of Biscay. Finally, the final spatial model estimated a strong movement from the northern area to the Celtic Sea. The final spatial model is a step towards a spatial assessment and management of the stock.

Prediction of silver hake distribution on the Northeast U.S. shelf based on the Gulf Stream path index

Over the past ~40 years, the distribution of silver hake on the Northeast U.S. shelf is found to be significantly correlated with changes in the latitude of Gulf Stream path. The correlation coefficient between the fall Gulf Stream position and the center of biomass of spring silver hake reaches 0.75 when the Gulf Stream leads the silver hake for 6 months. Based on this lead-lag relationship and low-frequency variability of Gulf Stream position with a dominant periodicity of ~9–10 years, the Gulf Stream position is used as a predictor for the center of biomass of silver hake in linear autoregressive (AR) models. The goal of this study is then to optimize the AR model for the prediction of silver hake based on the observed changes in Gulf Stream position. Fall Gulf Stream position is first predicted out to 5 years using a 5th order AR model and the observed Gulf Stream position in preceding years. An optimization process is proposed to choose best AR coefficients based on a newly proposed combined skill parameter. Furthermore, the robustness of our Gulf Stream prediction is verified by comparing the observed Gulf Stream path index data from 2009 to 2012, which are not used for optimizing the AR model, and the predicted Gulf Stream path values for the same time period. We then use this predicted Gulf Stream position to further predict the center of biomass of silver hake in the subsequent spring. Three different methods are used and compared for the silver hake prediction. The predicted silver hake time series can explain as much as 69% of the variance of the observation for the 1st year prediction and 41% for the 5th year prediction. Our results indicate that including Gulf Stream as a predictor produces better prediction skills of silver hake center of biomass than the AR model prediction solely based on the observed silver hake time series.

Silver hake tracks changes in Northwest Atlantic circulation

Recent studies documenting shifts in spatial distribution of many organisms in response to a warming climate highlight the need to understand the mechanisms underlying species distribution at large spatial scales. Here we present one noteworthy example of remote oceanographic processes governing the spatial distribution of adult silver hake, Merluccius bilinearis, a commercially important fish in the Northeast US shelf region. Changes in spatial distribution of silver hake over the last 40 years are highly correlated with the position of the Gulf Stream. These changes in distribution are in direct response to local changes in bottom temperature on the continental shelf that are responding to the same large scale circulation change affecting the Gulf Stream path, namely changes in the Atlantic meridional overturning circulation (AMOC). If the AMOC weakens, as is suggested by global climate models, silver hake distribution will remain in a poleward position, the extent to which could be forecast at both decadal and multidecadal scales.

Hake catchability by the French trawler fleet in the Bay of Biscay: estimating technical and biological components

AbstractMahévas, S., Trenkel, V. M., Doray, M., and Peyronnet, A. 2011. Hake catchability by the French trawler fleet in the Bay of Biscay: estimating technical and biological components. – ICES Journal of Marine Science, 68: 107–118. Several factors affect trawl catchability: (i) gear and vessel technical characteristics, (ii) anthropogenic factors, and (iii) biological factors. The objectives of this study were to assess the relative contribution of each factor to variations in hake (Merluccius merluccius) landings by the French trawler fleet operating on the shelf of the northern Bay of Biscay (ICES Subdivision VIIIa). Using generalized linear models, the impact of technical and anthropogenic factors was evaluated using landings per unit effort (lpue) obtained from logbooks. Variations in hake lpue were explained primarily by anthropogenic factors. For studying the biological components of catchability, the results of a scientific trawl survey in July 2006 involving three similar trawlers of the French trawler fleet were used. Daytime accessibility to large hake was lower than at night, and about zero for small hake (<19 cm). Estimates of spatial variation made using generalized linear mixed models showed a patchy fine-scale spatial distribution, but a random larger-scale distribution of hake over the area surveyed.

Mislabeling of Two Commercial North American Hake Species Suggests Underreported Exploitation of Offshore Hake

AbstractMislabeling of North American merlucciid hakes in stock surveys and commercial market samples was detected by employing nuclear 5S ribosomal DNA (rDNA) and mitochondrial cytochrome b variation as molecular markers. Results showed that offshore hake Merluccius albidus is sold in European markets but is labeled as the morphologically similar silver hake M. bilinearis, which is the target species of the fishery. This suggests that offshore hake may be inadvertently included within silver hake landings, as the two species overlap in the southern area of silver hake distribution (approximately 41°‐35°N latitude near North American coasts). An inexpensive and technically easy technique based on polymerase chain reaction (PCR) amplification of a fragment of 5S rDNA and visualization of PCR products in agarose gels is recommended for routine species assignation in landings for purposes of exploitation estimates and for authentication of commercial hake species.

Identifying fish nurseries using density and persistence measures

We propose a 3-step methodological approach to identify and classify fish nurseries for fisheries management purposes. We applied our approach to juvenile European hake Merluccius merluccius in the central Mediterranean Sea. Time series of trawl-survey fish-density data were used to map juvenile hake distribution with Bayesian kriging, while geostatistical aggregation curves were used to find density hot-spots. Persistence measures were adopted to identify nurseries on the basis of their spatio-temporal persistence. We found that areas with a high density of juvenile hake showed a high temporal persistence on both a seasonal and annual basis, with the most persistent nursery areas covering about 5% of the study areas while including about 39% of hake recruitment (averaged over 10 yr). We believe the persistence of these areas is indirect evidence of their impor- tance to the productivity of the population, with many potentially important implications for fisheries management. The approach that we developed to identify hake nurseries can be applied to different species and life stages to improve knowledge of the role of habitat for populations and communities.

Identification of hake distribution pattern and nursery grounds in the Hellenic seas by means of generalized additive models

A time series of hake abundance data obtained from the “MEDITS” experimental surveys carried out in the Greek seas from 1996 to 2006 have been modeled by means of Generalized Additive Models (GAMs), as functions of spatial and temporal variables, including sampling position (latitude–longitude interaction), depth, and year. All variables were highly significant but most of the variation was explained by the sampling position and the depth. Total abundance was higher in the 100–450 m depth zone, while juveniles showed preference for shallower waters, being more abundant from 100 to 320 m. Model predictions were used to generate density distributions maps, which revealed that total abundance is relatively higher in the western part of the Aegean Sea and in the eastern part of the Cretan Sea, while its maximum values are expected in the Saronikos Gulf. Nursery grounds are restricted in specific regions with the most important of them being in the Saronikos Gulf and its surrounding area.

The influence of oceanographic scenarios on the population dynamics of demersal resources in the western Mediterranean: Hypothesis for hake and red shrimp off Balearic Islands

The aim of the present paper is to study the relationships between some climatic indices and parental stock, recruitment and accessibility to trawl fishery of hake ( Merluccius merluccius) and red shrimp ( Aristeus antennatus) off Balearic Islands (western Mediterranean). Available annual catch per unit effort, recruitment and spawning stock biomass have been used as biological data. As environmental data, the meso-scale IDEA index and the large-scale North Atlantic Oscillation (NAO) and Mediterranean Oscillation (MO) indices have been used. To analyze possible links between these indices with the population dynamics of demersal resources, two non-linear approaches have been applied: (i) stock–recruitment relationships from Ricker and Beverton–Holt models, by sequentially incorporating environment factors; (ii) generalized additive modelling, both classical general and threshold non-additive models were considered. The latter simulate an abrupt change in explicative variables across different phases (time periods or climatic index values). The results have shown that two oceanographic scenarios around the Balearic Islands, associated with macro and meso-scale climate regimes, can influence the population dynamics of hake and red shrimp. This is especially true for recruitment, which seems to be enhanced during low NAO and IDEA indices periods. During these periods, colder-than-normal winters generate high amounts of cold Western Mediterranean Intermediate Waters (WIW) in the Gulf of Lions, which flow southwards and reach the Balearic Islands channels in spring, increasing the productivity in the area. This oceanographic scenario could also be favourable to the distribution of hake on the fishing grounds where the trawl fleet targets this species, increasing its accessibility to the fishery. Both spawning stock and abundance of red shrimp seems to be also enhanced by high MO index periods, which could reflect the increased presence of the saline and warm Levantine Intermediate Waters (LIW) in the study area, extending over the fishing grounds of this species. The proposed interactions can be useful to assess and manage these important demersal resources.

The relationship between Pacific hake (Merluccius productus) distribution and poleward subsurface flow in the California Current System

In a search for ocean conditions potentially affecting the extent of Pacific hake (Merluccius productus) feeding migrations, we analyzed data collected in 1995 and 1998 by the National Marine Fisheries Service on abundance and distribution of hake (by echo integration), intensity and distribution of alongshore flow (from acoustic Doppler current profiler), and temperature (conductivity–temperature–depth profiles). Our results show that Pacific hake are associated with subsurface poleward flow and not a specific temperature range. Temporal and spatial patterns characterize both hake distribution and undercurrent characteristics during the two years of this study. We suggest that poleward flow in this area defines adult hake habitat, with flow properties aiding or impeding the poleward migration of the population. We conclude that although physical processes may not directly affect fish production, they may be the link between large-scale ocean–atmosphere variability and pelagic fish distribution.

Remotely sensed local oceanic thermal features and their influence on the distribution of hake ( Merluccius hubbsi) at the Patagonian shelf edge in the SW Atlantic

We propose a new index based on sea surface temperature that can be used to locate local oceanic thermal features. The concept of relative spatial variability of local SST (SST RV), and the algorithm used to derive it, are introduced. The utility of this index is compared with that of SST gradient in an analysis of environmental correlates of the distribution and abundance of the hake Merluccius hubbsi (Marini, 1933) on the Patagonian shelf edge between 44.5°S and 47.0°S and around the Falkland Islands (Islas Malvinas). The SST RV and SST gradient were calculated from AVHRR SST data. SST RV is suggested to be a more sensitive index than SST gradient for detecting local oceanic thermal features such as fronts. Local hake abundance varied between years and showed strong (albeit complex) relationships with depth and SST, as well as with parameters (SST RV and SST gradient) that indicate the presence of ocean surface thermal features. Although local hake abundance was positively correlated with both SST RV and SST gradient, the former correlation was stronger and in two out of three studied months SST RV was the better predictor of CPUE. Although CPUE tended to increase with SST RV, this relationship breaks down at the highest SST RV values, possibly because hake avoid the most turbulent waters.

Monitoring the Prestige oil spill impacts on some key species of the Northern Iberian shelf

Selected key components of the continental shelf benthic and demersal communities were monitored for the two years following the Prestige oil spill (POS) in order to identify the possible ecological effects of the oil. This work includes the first results regarding changes in abundance, distribution and food habits of hake ( Merluccius merluccius), four-spot megrim ( Lepidorhombus boscii), Norway lobster ( Nephrops norvegicus) and Pandalid shrimp ( Plesionika heterocarpus) populations of Galician and Cantabrian Sea shelves following the POS. Significant reductions in the abundance of Norway lobster, Plesionika heterocarpus and four-spot megrim were detected in the POS maximum impact area, located over the Galician shelf. Noteworthy recoveries were observed in the 2004 abundance indices of four-spot megrim and Plesionika. On the other hand, no significant effects were detected in the abundance or distribution of hake juveniles even though the tar aggregates were bound by the same oceanographic drift events as the hake recruits were during the winter of 2003 ( Navidad current) in different water column layers of the Cantabrian Sea. Feeding patterns of the four species analysed did not present apparent modifications that can be related to the POS.

Distribution and abundance of European hake Merluccius merluccius (L.), eggs and larvae in the North East Atlantic waters in 1995 and 1998 in relation to hydrographic conditions

Plankton samples from surveys in 1995 and 1998 were analysed in order to study the spatial distribution of hake (Merluccius merluccius) eggs and larvae. The cruises covered an extensive area from the south of the Bay of Biscay to the north-west of Ireland. This spatial distribution has been interpreted in relation to the direction and intensity of the dominant winds. An important decrease of eggs (69%) and larvae (27%) was observed from 1995 to 1998. Hake showed continuous spawning from February to July in the area. The centroids of hake egg distribution indicated a northward displacement of the peak of spawning as the season progresses. Spawning of hake was located close to the 200 m depth isobath in the southern area (Bay of Biscay) and it spread over the shelf in the area of the Celtic Sea. Eggs were most abundant at 20 m depth temperatures between 12 and 12.5°C. The centroids of hake larvae distribution also showed a northward displacement although not as strong as that of hake eggs. The spatial distribution of hake larvae by size ranges showed important differences between years: in 1995 it suggested inshore transport of larvae, from the spawning areas (close to the 200 m depth isobath) to nursery areas (closer to the coast) while in 1998 it suggested offshore transport. This transport does not correspond with the general wind regimes during those years. Therefore it is concluded that the transport of the hake larvae to nursery areas must be controlled by different hydrographic mechanisms such as geostrophic currents in the Bay of Biscay and tidal currents in the northern areas.

Distribution of hake ( Merluccius merluccius, Linnaeus, 1758) in the Bay of Biscay and the Celtic sea from the analysis of French commercial data

Hake landings and effort data provided by the French otter trawl fleets exploiting the Celtic sea and Bay of Biscay fishing grounds were used for years 1992–1994. Monthly catch rates of five hake weight market categories were calculated and used as input in a correspondence analysis and hierarchical ascending classification procedure to describe the spatio-temporal distribution of hake in the Celtic sea and the Bay of Biscay. Results show a great difference in hake catch composition between the two zones. The higher proportion of small hake in the Bay of Biscay can be explained by the use of a minimum mesh of size 65 mm instead of 80 mm in the Celtic sea and the existence of a hake nursery coinciding with the muddy bottom of Nephrops fishing grounds in the northern part of the Bay of Biscay. Adult hake were found relatively more abundant in the shallow water of the eastern Celtic shelf from April to November. Oldest fish seemed to move westwards at the end of the year. They congregate for spawning along the slope and on the shelf in the north-western part of the Celtic sea from February to April–May. There is no evidence that young adult hake follow the same migratory pattern but they were found in abundance along the slope in the north of the Bay of Biscay during autumn and winter months.