Bottom Trawl Surveys Research Articles

Grooved tanner crab <i>Chionoecetes tanneri</i> in the north-western Bering Sea: criteria for choosing the optimal fishing measure

Spatial and bathymetric distribution and aggregation density is considered for bathyal crabs, including the grooved tanner crab <i>Chionoecetes tanneri</i>, on the data of specialized deep-water trap survey and two bottom trawl surveys within the depth range of 300‒1080 m conducted by TINRO in the northwestern Bering Sea in 2019–2020. The size of grooved tanner crab is determined as 9.0–17.0 cm for the morphometrically mature males and 6.5–15.5 cm for the morphometrically immature males, by carapace width. The size of 50 % morphometric maturity is evaluated for males of <i>Ch. Tanneri</i> in the northwestern Bering Sea. A new fishing measure is substantiated for this population taking into account its size composition.

Influencing factors of predation on five keystone prey species in Haizhou Bay based on Delta-GAMMs.

Trophic dynamics is one of the major regulators of fishery production in marine ecosystems, which is important for the implementation of ecosystem-based fisheries management. Based on data collected form bottom trawl surveys in Haizhou Bay and adjacent waters during autumn of 2011 and 2018, Delta-GAMMs (Delta-generalized additive mixed models) were constructed to evaluate the effects of biotic and abiotic factors on the predation of five key prey species (including Leptochela gracilis, Alpheus japonicus, Loligo spp., Larimichthys polyactis, and Oratosquilla oratoria) in the Haizhou Bay. Percent frequency of occurrence and predation pressure index were used to identify their major predators. Variance inflation factor and full subsets regression were analyzed to quantify the degree of multicollinearity between these factors. The results showed that the occurrence frequency of keystone prey species in the stomach of predators ranged from 8.5% to 42.2%, and the weight percentage ranged from 4.2% to 40.9%. The average deviance explanation rate of the "binomial" model was 16.1%, and the average deviance explanation rate of the "positive" model was 23.8%. Body length of predator, predator population density, and sea bottom temperature were important factors influencing prey-predator trophic interactions. Predator length was the most important factor, with feeding probability and weight percentage of keystone prey species all increasing with body length of predator. Feeding probability and weight percentage of key prey species decreased with predator population density. The effects of environmental factors such as sea bottom temperature, depth of water, latitude, and sea bottom salinity showed different trends, depending on the prey-predator assemblage. This study showed that the Delta-GAMMs was an effective method to explore the trophic interactions between prey and predators in marine ecosystems, and could provide a theoretical basis for the conservation and sustainable use of fisheries resources.

Trends in Area of Occurrence and Biomass of Fish and Macroinvertebrates on the Northeast U.S. Shelf Ecosystem

AbstractClimate change can affect the habitat of marine species and hence their persistence and adaptation. Trends in area of occurrence and population biomass were examined for 177 fish and macroinvertebrates resident to the Northeast U.S. Continental Shelf ecosystem. Samples of these organisms were taken during a time series of research bottom trawl surveys conducted in the spring and autumn 1976–2019. The occurrence area of each taxon was modeled as the distribution of occurrence probability based on a random forest presence/absence classification model. Following, a population biomass of each taxon was modeled as a minimum swept area estimate, where the ecosystem was stratified biannually based on each taxon's spatial distribution. In both seasons, the sum of occurrence area and biomass across all modeled species increased over the study period. The summation of biomass is problematic since catchability is not known for most species; more importantly, most time series of individual species biomass trended higher. We found that the ratio of biomass to occurrence area, intended as a measure of productivity, showed no change in the autumn and had a weak increasing trend in spring. For the majority of taxa, the rate of change in biomass tracked changes in occurrence area (either positive or negative), but there were cases where the direction of change in biomass was opposite to the direction of change in occurrence area. Thermal conditions in surface waters appear to be a more important driver of occurrence area and biomass change than the change in thermal conditions near the bottom. These findings provide critical insights into the expected changes in ecosystem productivity transpiring with climate change.

Developing a subseasonal ecological forecast to reduce fisheries bycatch in the Northeast U.S.

Over the past decade, substantial progress has been made in projecting and predicting the spatial distribution of many marine species at seasonal to multidecadal time scales. However, managers and fishers often need to make decisions at much shorter time scales. Subseasonal environmental forecasts, which generate predictions over one to several weeks, can now be combined with species-specific habitat preference data to create ecological forecasts that could facilitate dynamic spatial management. The development of such predictive tools could aid in identifying optimal times and areas for fishers to maximize target catch and avoid nontarget catch. Nontarget catch, or bycatch, can have numerous and potentially severe economic and ecological consequences. Here, we focus on a population of anadromous fish known collectively as river herring (alewife and blueback herring), as they are species of concern and are heavily impacted by bycatch. Using bottom trawl survey data from the Northeast US and subseasonal forecasts of sea surface temperature, we constructed a bycatch risk model to generate probabilistic predictions of river herring distributions in regions frequented by the US mid-water trawl fishery. Assessments of model skill showed that our ecological model performed well in predicting the distribution of river herring and that subseasonal forecasts were effective at 1-week timeframes. There was a clear seasonal effect on forecasted bycatch risk throughout the Northeast US, with particularly high risk in winter and spring months. Importantly, variability in risk was detectable at the weekly timescale and our model identified specific areas and times that fishers should avoid in order to decrease their likelihood of bycatch. The bycatch risk forecast developed in this study is a significant advance from near-real time forecasts and the foundation to build forecast systems by combining species co-occurrence models with subseasonal forecasts. As these subseasonal forecasts are available globally, this approach could be adapted to facilitate the management of other natural resource conflicts around the world.

Blondes do it better? A comparative study on the morphometry and life-history traits of commercially important skates blonde ray Raja brachyura, thornback ray Raja clavata, and spotted ray Raja montagui, with management implications

Due to data limitation and challenges with species-specific reporting, the management of European skate fisheries currently lacks measures tailored to individual species. Given these caveats, detailed information about skate stocks at the species level is warranted. The morphometry and life-history parameters were determined for samples of 170 individuals (58 Raja brachyura, 92 R. clavata, 20 R. montagui) collected by observers in commercial fisheries, and two bottom trawl surveys (December 2020 – August 2021) in the Southern North Sea and Eastern English Channel. A combination of three morphometric measurements were considered and proven successful (3.846% misclassification, N = 78) in species discrimination for easily confusable species R. brachyura and R. montagui. Through the application of these morphometric descriptors in electronic catch monitoring via Artificial Intelligence (AI), the misidentification of easily confusable species may be reduced in future catch reporting from surveys, fisheries-dependent data, and market sampling. Additionally, the morphometric differences between species may have implications for species’ catchability, and gear modification to avoid bycatch of skates under the European Landing Obligation (LO). The length-weight relationships indicated a faster rate of increase in body mass per unit of size for R. montagui. Life-history trait parameter estimates were obtained for R. clavata and R. brachyura. Age was determined through digital processing of images from visually enhanced whole vertebral centra (0.01% crystal violet staining). Age reading precision was low (CV > 45%, PA < 60%). The von Bertalanffy and logistic growth models provided more accurate fits for the length-at-age data than the Gompertz model. Macroscopic maturity assessment revealed that male R. montagui matured at the smallest size (Lm = 57.5 cm), while female R. brachyura matured at the largest size (Lm = 87.6 cm). Maturity ogives were fitted for males (L50 = 65.4 cm) and females (L50 = 84.1) of R. clavata and females of R. brachyura (L50 = 82.7 cm), with statistically significant intersexual differences for R. clavata. The Legal Minimum Landing Size (LMLS) measures of smaller sizes may not offer adequate protection (to immature specimens) of the skate species in the present study, that mature at larger sizes. The life-history trait parameters for growth and maturity are discussed in relation to published results of earlier studies, and no major changes in the life-history parameter traits were observed in recent years. The interspecific differences in the morphometries and life-history traits of R. brachyura, R. clavata, and R. montagui highlight the need for species-specific data collection and management considerations of skate stocks in the Northeast Atlantic Region at the local and EU level.

Variations in fish community composition and trophic structure under multiple drivers in the Beibu Gulf

IntroductionBeibu Gulf is a semi-enclosed bay with important ecological and economic value of the northwestern South China Sea (SCS). It proved to be a stressed ecosystem and therefore clearly vulnerable to further external disturbances.MethodsData from 26 fishery bottom trawl surveys in the Beibu Gulf from 2006 to 2018 are analyzed to reveal changes in the fish abundance, dominant species composition, diversity, mean trophic level (MTL), and fishing-in-balance (FiB) index.ResultsFish abundance decreased significantly (p&amp;lt; 0.05) with increased anthropogenic disturbance (e.g., fishing intensity and land-derived pollutants), with catch per unit effort (CPUE) decreasing from 40.69 kg·h−1 in 2006 to 15.84 kg·h−1 in 2018. Dominant species composition has changed dramatically from 2006 to 2018, with fish communities shifting from demersal to pelagic species, and from large and high-trophic-level species to small and low-trophic-level species. Meanwhile, Margalef’s richness and Shannon–Wiener diversity indexes trend downward. The MTL declines from 3.82 in 2006 to 3.71 in 2018 (at 0.08 trophic level per decade), and decreasing with the decrease of the proportion of high-trophic fish and demersal fish in total catch (p&amp;lt; 0.05). A FiB index tends to be less than 0, this index declines with decreasing MTL and fish abundance (p&amp;lt; 0.05).DiscussionOverall, fish stocks in the Beibu Gulf continue to decline and are currently overexploited. Multiple external disturbances, such as fishing (including overfishing, dominance of trawl fishery, and ‘skipper effect’), habitat disturbance, pollution, and temperature changes, may have contributed to significant changes in fish communities and trophic structure in the Beibu Gulf.

Distribution of Dragon Poacher Percis japonica (Agonidae) in the Russian Territorial Waters in the Sea of Japan

The research outcomes of spatial and bathymetric distribution of dragon poacher Percis japonica are reported based on the bottom trawl surveys carried out in the Russian territorial waters in the Sea of Japan. The species can be found in the waters along the entire coastline. However, its spatial distribution pattern is variable. Thus, its distribution is sparse off the coasts of West Sakhalin, especially off the southern part of the island, while the species tends to congregate in the Peter the Great Bay and the Tatar Strait, where the locations of the species across these water areas remain almost unchanged throughout the year. With respect to the Northern Primorye Coastal Zone, the even distribution is typical for the entire water area, without any high congregation locations. Therefore, the dragon poacher can be found in wide ranges of depths and temperatures. However, its preferable ranges are substantially narrower. The highest values for available biomass resources are typical for the water areas off the Northern Primorye Coastal Zone.

Distribution and life strategy of the deep-sea crab Paromola cuvieri (Risso, 1816) (Brachyura, Homolidae) in the central Mediterranean Sea over twenty-five years

The present study represents a new contribution to the knowledge on the distribution and life strategy of P. cuvieri in the central Mediterranean. During 71 experimental bottom trawl surveys carried out in the Northern Ionian Sea from October 1994 to July 2019 a total of 457 specimens was sampled from 91 to 1118 m in depth. The highest frequency of occurrence and density was observed in the 600–800 m depth range. The relationship between carapace length and depth was statistically significant showing a significant decrease in size with depth. The length-frequency distribution was unimodal for both sexes and there was a low number of small individuals. The most represented size classes for both sexes were between 50 and 130 mm Carapace Length (CL), with males significantly larger than females. The sex ratio by size showed an increase of males with increasing length. Of the sampled females, 50 were in ovigerous condition and 92 females were non ovigerous. P. cuvieri appears to have continuous reproduction throughout the year, with ovigerous females observed in all seasons, with the highest abundance in spring and winter and between 400 and 800 m of depth. The fecundity ranged between 138165 and 374453 eggs with a mean value of 217237 eggs. The eggs show a spherical shape and their mean size increased with maturity stage. Egg development appears to not be completely synchronous, and two patterns can be observed simultaneously. The relationships between CL/brood size and weight/brood size were highly significant. The relationships between width and hand-length of both chelae and Carapace Width (CW) for both sexes were highly significant. Time-series data showed a scanty abundance of P. cuvieri in the studied area with no trend over the period 1995–2019 with no significant trend over. Its preferential distribution on the middle slope was confirmed. Time-series data (1995-2019) showed a scanty abundance of P. cuvieri in the studied area with no signficant trend. Its preferential distribution on the middle slope was confirmed.

Information on the deep-water giant red shrimp Aristaeomorpha foliacea (Risso, 1827) (Crustacea, Decapoda, Aristeidae) population in Antalya Bay (Eastern Mediterranean Sea, South of Turkey) based on the MEDITS protocol

The main aim of this study was to contribute to the current knowledge on the population of Aristaeomorpha foliacea in Antalya Bay located on the southern coast of Turkey in the Mediterranean Sea. Monthly samples were collected between July 2016 and July 2017 from experimental trawl surveys in accordance with the International Bottom Trawl Survey in the Mediterranean (MEDITS) protocol. The abundance index was calculated as 4308.6 N/km 2 and the biomass index as 66.8 kg/km 2. The relationship between total weight (TW) and carapace length (CL) was estimated to be TW = 0.00078⋅CL2.76 for females and TW=0.00049⋅CL2.92 for males. The seasonalized von Bertalanffy growth parameter estimates were CL∞=66.12mm, K=0.43 years −1, tanchor=0.36 years, C=0.63 and ts=0.21 years for females, and CL∞=44.02mmK=0.39 year −1, tanchor=0.30 years, C=0.77 and ts=0.87 years for males. Female shrimps grew slightly faster and reached a larger asymptotic size hence exhibiting a greater growth performance than males. The spawning season was determined as the summer. Recruitment took place in spring, and the sex ratios were found to be 1.29:1 in favor of males. The median size at first maturity was estimated as 37.7 mm CL for females and 30.1 mm CL for males. The annual total mortality rate was 1.66 and 1.41, the annual natural mortality rate 0.57 and 0.72, and the exploitation rate 0.66 and 0.49 for females and males, respectively. The fishing ground for A. foliacea in Antalya Bay is situated within 12 nautical miles off the shore within the territorial waters, thus closed to commercial trawl fisheries between 15 April and 15 September in accordance with the Turkish fishery regulations. The closing period, which coincides with the spawning season and also provides a reduction in the fishing pressure, is clearly of great importance for the sustainability of this species in Antalya Bay.

The Role of Fishery‐Independent Bottom Trawl Surveys in Providing Regional and Temporal Context to Offshore Wind Farm Monitoring Studies

AbstractBottom trawl surveys are commonly used to examine potential effects on fishes and invertebrates from offshore wind (OSW) farms in Europe and in the northeastern United States. Because OSW surveys typically occur over a limited spatial footprint, comparison of OSW monitoring results to long‐term fishery‐independent surveys may provide a regional and temporal context for OSW data sets. We compared results of the Block Island Wind Farm (BIWF) bottom trawl survey (2013–2019) to three fishery‐independent bottom trawl surveys (Northeast Area Monitoring and Assessment Program, Northeast Fisheries Science Center, and Rhode Island Department of Environmental Management [RIDEM]) using catch rates of 12 federally managed species. We evaluated temporal trends in annual residual catches for each species calculated within each survey as the difference between the mean annual biomass per trawl and the long‐term mean. Regional consistency in relative catches was apparent for species exhibiting synchronous interannual variability among surveys (Black Sea Bass Centropristis striata, Scup Stenotomus chrysops, Summer Flounder Paralichthys dentatus, and Winter Flounder Pseudopleuronectes americanus) or a decreasing trend in residual catch rates across the 7‐year study period (Little Skate Leucoraja erinacea, longfin inshore squid Doryteuthis pealeii, and Winter Skate L. ocellata). For other species, catches among surveys were asynchronous (Atlantic Herring Clupea harengus, Butterfish Peprilus triacanthus, and Windowpane Scophthalmus aquosus) or anomalous catches in a single year affected the results (Red Hake Urophycis chuss and Silver Hake Merluccius bilinearis). Monitoring of BIWF occurred during a period with lower‐than‐average historical catches in a 32‐year RIDEM data set for Atlantic Herring, Butterfish, Little Skate, longfin inshore squid, Red Hake, Silver Hake, and Winter Flounder and higher‐than‐average catches for Black Sea Bass, Scup, and Summer Flounder. There was no evidence that variation in catches near BIWF differed from regional trends in a way consistent with a detrimental impact of OSW farm operation. The regional context provided from multiple bottom trawl surveys varies by species and thus may be limited for interpreting OSW monitoring results.

Spatiotemporal distribution of Lophius litulon in the southern Yellow Sea and East China Sea

In order to investigate the temporal-spatial distribution of yellow goosefish in the open waters of the southern Yellow Sea (SYS) and East China Sea (ECS), according to the fishery data by bottom-trawl surveys and environmental data including sea bottom temperature (SBT), sea bottom salinity (SBS), bottom concentration of dissolved oxygen (BDO) and depth during 2018-2019, we established habitat suitability index (HSI) models by arithmetic mean (AMM) and geometric mean (GMM) methods, and compared the model outputs by cross validations. Especially, the weight of each environmental factor was evaluated by boosted regression tree (BRT). Results showed that the area with the highest habitat quality varied among seasons. The yellow goosefish mainly inhabited in the adjacent area of the Yangtze River Estuary and coastal waters of Jiangsu Province with depth ranged from 22 to 49 m in spring. The optimal inhabitation was located in the SYS, with the bottom temperature ranged from 8.9-10.9 ℃ in summer and autumn. Particularly, the optimal inhabitation extended from the SYS to the ECS with bottom temperature ranged from 9.2-12.7 ℃ in winter. Results of BRT models showed that depth was the most important environmental factor in spring and bottom temperature was the crucial one in the other three seasons. Results of cross validation showed that the weighted AMM-based HSI model performed better for yellow goosefish in spring, autumn and winter. The distribution of yellow goosefish was closely related to its biological traits and environmental factors in the SYS and ECS, China.

First record of the cirripede Anelasma squalicola Darwin, 1852 (Pollicipedidae) in the Mediterranean Sea

Anelasma squalicola Darwin 1852, is a barnacle that occurs on elasmobranchs from the Atlantic, Pacific, Arctic and Indian Ocean. It infects sharks of the families Etmopteridae and Pentanchidae. The barnacle attaches sub-dermally to its hosts, relying on its interstitial fluid for its nourishment. Herein we present the first record of this species in the Mediterranean Sea, from Etmopterus spinax (Linnaeus, 1758) caught during a bottom-trawl survey in the Alboran Sea (western Mediterranean) in 2017. The overall prevalence of infection was very low (0.22%). The calculated HSI index for the parasitized individual was lower compared to overall means of other individuals and could indicate a potential physiological alteration in the host.

Some data on the fishery, distribution and size composition of saffron cod Eleginus gracilis Tilesius, 1810 near the Southern Kuril Islands

Data on harvesting, seasonal dynamics, structure of coastal and marine fishery, size and age composition of saffron cod catches near the Southern Kuril Islands are given. Summer–autumn distribution and size composition of saffron cod aggregations is considered based on the data of bottom trawl surveys. Distribution of saffron cod is shown almost everywhere near Kunashir Island, the Lesser Kuril Ridge and Pacific coast of Iturup Island. Harvesting is provided throughout the year, but mainly at December fishing for bottom and demersal fish species in the South Kuril Strait and May–June fishing with small fixed nets near Kunashir. Although catches of saffron cod have increased in recent years, the species is still under exploited commercially.

Incorporating distribution shifts and spatio-temporal variation when estimating weight-at-age for stock assessments: a case study involving the Bering Sea pollock (Gadus chalcogrammus)

AbstractEnvironmental conditions can create spatial and temporal variability in growth and distribution processes, yet contemporary stock assessment methods often do not explicitly address the consequences of these patterns. For example, stock assessments often assume that body weight-at-age (i.e. size) is constant across the stocks’ range, and may thereby miss important spatio-temporal patterns. This is becoming increasingly relevant given climate-driven distributional shifts, because samples for estimating size-at-age can be spatially unbalanced and lead to biases when extrapolating into unsampled areas. Here, we jointly analysed data on the local abundance and size of walleye pollock (Gadus chalcogrammus) in the Bering Sea, to demonstrate a tractable first step in expanding spatially unbalanced size-at-age samples, while incorporating fine-scale spatial and temporal variation for inclusion in stock assessments. The data come from NOAA’s bottom trawl survey data and were evaluated using a multivariate spatio-temporal statistical model. We found extensive variation in size-at-age at fine spatial scales, though specific patterns differed between age classes. In addition to persistent spatial patterns, we also documented year-to-year differences in the spatial patterning of size-at-age. Intra-annual variation in the population-level size-at-age (used to generate the size-at-age matrix in the stock assessment) was largely driven by localized changes in fish size, while shifts in species distribution had a smaller effect. The spatio-temporal size-at-age matrix led to marginal improvement in the stock assessment fit to the survey biomass index. Results from our case study suggest that accounting for spatially unbalanced sampling improved stock assessment consistency. Additionally, it improved our understanding on the dynamics of how local and population-level demographic processes interact. As climate change affects fish distribution and growth, integrating spatiotemporally explicit size-at-age processes with anticipated environmental conditions may improve stock-assessment forecasts used to set annual harvest limits.

Using predator diets to infer forage fish distribution and assess responses to climate variability in the eastern Bering Sea

Forage fishes comprise an integral part of marine food webs in the highly productive ecosystems of the North Pacific. However, significant knowledge gaps exist related to the status of forage fish, their life histories, and how populations may react to future climatic shifts. Standardized bottom trawl surveys are critical to the stock assessment of groundfish but lack the gear and protocols to quantitatively evaluate small pelagic forage fish. Where diet data are available, predators may be used as an indirect method of collecting data on forage fish distribution and relative abundance. We used stomach contents data to infer predator-prey interactions in the eastern Bering Sea and to analyze the distribution of 5 forage taxa over a 34 yr time series (1985-2019). Using 4 dominant groundfish predators, we constructed forage fish and predator depth and temperature habitat profiles and used center of gravity (COG) analysis and global index of collocation to examine predator-prey overlap. Results provide insight on the habitat partitioning and competitive interactions between forage species and the dynamics between predators and prey. Interannual COG analyses indicated recent periods of cooling (2007-2013) and warming (2014-2019) had significant effects on the distribution of forage fish, and suggest differences in the relative resilience of forage fish populations to climate change in this region. Population shifts were particularly evident in recent periods of anomalous warming, highlighting the need to understand how future periods of prolonged warming may affect predator-prey dynamics. Results also demonstrate the importance of predator diet time series and how these data might inform multi-species models and management strategies.

Growth as a measure for environmental conditions and relatedness of North Sea fish stocks

Information about the ecological connections between species is needed to make the shift from fisheries management strategies centred around single species to ecosystem-based fisheries management. Growth rates of fish strongly depend on the environment. Individual growth curves could therefore contain valuable information about the environmental conditions experienced by an individual throughout its life. In this study, we explored whether estimated growth curves contain information about the competition within and between species. We estimated growth curves for 10 species in 10 North Sea roundfish areas based on length-at-age data from the North Sea International Bottom Trawl Survey (NS-IBTS) fish survey by fitting a von Bertalanffy growth model with varying asymptotic length. From these model fits, we extracted a relative measure for the temporal variation in growth in body size of a stock, which can be used as an indicator of the experienced environmental conditions. We found signs of density-dependent growth in at least 6 out of the 10 species for some specific areas as well as all North Sea areas combined. In addition, we used cluster analysis to explore the relatedness in ecological growth conditions between species and areas. Ecologically related species tended to show more similar temporal variation in ecological growth conditions than ecologically more distant species. Likewise, areas that were geographically closer showed more similarity in ecological growth conditions compared to geographically more distant areas. This suggests that information on ecological conditions derived from growth curves provide a useful way to distinguish ecological groups or regions without the need for additional stomach sampling or ecological studies.

Assessing individual movement, habitat use, and behavior of non-breeding marine birds in relation to prey availability in the US Atlantic

Resource availability is a key factor driving marine bird movements and distributions, but direct information on prey availability is difficult to obtain at relevant scales. We present novel methods for describing multi-scale trophic associations, combining movement analyses of marine birds with estimates of forage fish surface aggregations from digital aerial survey data and species occupancy from bottom trawl survey data. We analyzed satellite telemetry data from northern gannets Morus bassanus, red-throated loons Gavia stellata, and long-tailed ducks Clangula hyemalis in the US Atlantic during the non-breeding period. Using discrete-time hidden Markov models to distinguish area-restricted (i.e. putative foraging) from transit movements, we examined how environmental factors influence movement, and how forage fish species distributions and surface aggregations influence habitat use by gannets and loons that have greater dietary reliance. Our results suggest that chlorophyll a concentration significantly affected movement behavior across species, highlighting the importance of higher-productivity areas around estuaries during colder months when regional productivity is low. Though variable across species and seasons, spatial cross-correlation analysis revealed that herring species (Family Clupeidae), including Atlantic menhaden Brevoortia tyrannus, may be important resources; it also showed positive spatial correlations with forage fish aggregations. This suggests that prey patch dynamics and factors driving aggregation formation may be as important as species composition. However, spatial patterns were generally low (&lt;0.3), suggesting a mismatch in spatiotemporal resolution, exemplifying the challenges in quantifying trophic relationships in marine systems. Disentangling predator-prey relationships is critical to understanding the mechanisms driving marine bird behavior in rapidly changing marine systems.

Spatiotemporal patterns in the ecological community of the nearshore Mid-Atlantic Bight

Recognition of the need for a more holistic, ecosystem approach to the assessment and management of living marine resources has renewed interest in quantitative community ecology and fueled efforts to develop ecosystem metrics to gain insight into system status. This investigation utilized 12 years (2008 to 2019) of fisheries-independent bottom trawl survey data to quantify and synthesize the spatiotemporal patterns of species assemblages inhabiting the nearshore Mid-Atlantic Bight (MAB). Assemblages were delineated by ecomorphotype (EMT), and all species collected by the survey were allocated among 9 EMTs: demersal fishes; pelagic fishes; flatfishes; skates; rays; dogfishes; other sharks; cephalopods; and benthic arthropods. Annual time series and seasonal spatial distributions of relative aggregate biomass were quantified for each EMT using delta-generalized additive models. Dynamic factor analysis (DFA) revealed that the information content of the 9 annual time series was effectively summarized by 3 common trends, and DFA model fits to each EMT time series represented a new suite of ecosystem indicators for this system. Mean sea surface temperature during winter in the MAB was included in the selected DFA model, suggesting that winter environmental conditions influence the structure of this system at an annual scale. Principal component analysis uncovered a north-to-south gradient in the seasonal spatial distributions of these EMTs and identified a distinct area of elevated biomass for several assemblages along the south shore of Long Island, NY. Taken together, these results characterize the community structure of the nearshore MAB and yield requisite information to support ongoing ecosystem-scale assessment and management activities for this region.

Brief results of biological studies of the northern part of the Sea of Japan in the spring of 2022

The purpose of the work is a commercial and biological assessment of basic invertebrate species and other aquatic organisms in the northern regions of the Sea of Japan. Studies provide current characteristics of many commercial populations of bottom hydrobionts inhabiting depths of 24–611m.The material and methods are standard for fisheries research in Russia. Materials were collected in 29.04.-01.06.2022, in bottom trawl survey. The main objects of Decapoda research are commercial species of crabs and shrimps, as well as other species of hydrobionts.The new data revealed the following: 1) among crabs, the commercial stock increased slightly everywhere in Paralithodes camtschaticus, but it also decreased everywhere in P. platypus and Chionoecetes opilio, and in the crab Erimacrus isenbeckii, there was a significant increase only in Western Sakhalin; 2) among shrimps, the commercial stock increased everywhere in Pandalus borealis and P. hypsinotus, and in P. goniurus increased in the north of the Primorye subzone, but decreased in Western Sakhalin; 3) the biological condition and stock of other commercial invertebrates and fish of the bottom complex was satisfactory or a slight increase in their numbers was noted.The practical significance of the research is to provide fishing and biological information for annual prognostic materials on the total allowable catches of bottom commercial species of hydrobionts for the areas of the northern part of the Sea of Japan.

Distributions of Cisco (Coregonus artedi) in the upper Great Lakes in the mid-twentieth century, when populations were in decline.

The restoration of the once abundant Cisco (Coregonus artedi) is a management interest across the Laurentian Great Lakes. To inform the restoration, we (1) described historical distributions of Cisco and (2) explored whether non-indigenous Rainbow Smelt (Osmerus mordax) and Alewife (Alosa pseudoharengus) played a role in the decline of Cisco populations across the upper Great Lakes (i.e., Lakes Superior, Michigan, and Huron). Our source data were collected from fishery-independent surveys conducted by the U.S. Fish and Wildlife Service's research vessel R/V Cisco in 1952-1962. By analyzing data collected by gill-net surveys, we confirmed the importance of embayment and shallow-water habitats to Cisco. We found that Cisco was abundant in Whitefish Bay and Keweenaw Bay, Lake Superior, and in Green Bay, Lake Michigan, but we also found a sign of Cisco extirpation in Saginaw Bay, Lake Huron. Our results also showed that Ciscoes generally stayed in waters <80 m in bottom depth throughout the year. However, a substantial number of Ciscoes stayed in very deep waters (>150 m in bottom depth) in summer and fall in Lake Michigan, although we cannot exclude the possibility that these Ciscoes had hybridized with the other Coregonus species. By comparing complementary data collected from bottom-trawl surveys, we concluded that the spatiotemporal overlap between Rainbow Smelt and Cisco likely occurred across the upper Great Lakes throughout 1952-1962. These data were consistent with the hypothesis that Rainbow Smelt played a role in the decline of Cisco populations across the upper Great Lakes in the period. We also found that the spatiotemporal overlap between Alewife and Cisco likely occurred only in Saginaw Bay in fall 1956 and in Lake Michigan after 1960. Thus, any potential recovery of Cisco after the 1950s could have been inhibited by Alewife in Lakes Michigan and Huron.