Fishery-independent Trawl Surveys Research Articles

Remarkable shifts in the megabenthic community structure over four decades in Tokyo Bay, Japan, in relation to environmental variations

We investigated long-term changes in the megabenthic community in Tokyo Bay, Japan, using data from fisheries-independent trawl surveys conducted from 1977 to 2023. In addition, we examined the potential relationship between changes in biotic communities and environmental conditions. The total abundance and biomass exhibited an increasing trend until 1987, followed by a substantial decline from the late 1980s to the 1990s due to a decrease in small to medium-sized fish and crustacean species. Meanwhile, a marked increase in the number of large fish (including elasmobranchs), mollusks, and echinoids, was observed in the 2000s. These shifts in the megabenthic community structure were correlated with an increase in water temperature and a decrease in nutrient concentrations and copepod densities. Cumulative evidence suggests that a remarkable shift in the megabenthic community structure occurred between the 1970s and the 2020s, which was possibly associated with variations in the environmental conditions in Tokyo Bay.

Prevalence, intensity of infestation, and biomarker potential of the nemertean worm, Carcinonemertes carcinophila (Kölliker, 1845), on ovigerous blue crabs, Callinectes sapidus Rathbun, 1896 (Decapoda: Brachyura: Portunidae), in Chesapeake Bay, USA

Abstract The effect of individual and population-level egg mortality is important to quantify to maintain sustainable crustacean fisheries. The nemertean worm Carcinonemertes carcinophila (Kölliker, 1845) is an egg predator of the Atlantic blue crab, Callinectes sapidusRathbun, 1896; however, little is known about the impact this nemertean has on the reproduction of the blue crab. We assessed the prevalence and intensity of the infestation of nemerteans in ovigerous blue crabs using a fishery-independent trawl survey. During the primary spawning period of the crab, May–September 2022, 126 ovigerous females were collected and analyzed for worms. Prevalence over this time was 66.6% and mean brood infestation was 53.9 worms per infested crab host. Nemertean egg consumption was quantified with a six-day microcosm experiment. Of the 48 worms in the experiment, 71% actively fed on crab eggs and their consumption ranged 0.16–4.5 eggs day–1. Consumption rates were used to estimate population-level impact of nemertean feeding on crab brood mortality. Modeled proportions of brood loss per crab ranged 0–0.0044%. At the current prevalence and intensity of infestation, egg consumption by nemerteans has a negligible effect on blue crab reproductive output and batch fecundity in Chesapeake Bay. We also investigated the use of mature nemertean worms as a biomarker for establishing the spawning history of ovigerous female blue crabs and determined that the presence of worms in the clutch and in the gills can be used to indicate parity in ovigerous female crabs.

Groundfish biodiversity change in northeastern Pacific waters under projected warming and deoxygenation.

In the coming decades, warming and deoxygenation of marine waters are anticipated to result in shifts in the distribution and abundance of fishes, with consequences for the diversity and composition of fish communities. Here, we combine fisheries-independent trawl survey data spanning the west coast of the USA and Canada with high-resolution regional ocean models to make projections of how 34 groundfish species will be impacted by changes in temperature and oxygen in British Columbia (BC) and Washington. In this region, species that are projected to decrease in occurrence are roughly balanced by those that are projected to increase, resulting in considerable compositional turnover. Many, but not all, species are projected to shift to deeper depths as conditions warm, but low oxygen will limit how deep they can go. Thus, biodiversity will likely decrease in the shallowest waters (less than 100 m), where warming will be greatest, increase at mid-depths (100-600 m) as shallow species shift deeper, and decrease at depths where oxygen is limited (greater than 600 m). These results highlight the critical importance of accounting for the joint role of temperature, oxygen and depth when projecting the impacts of climate change on marine biodiversity. This article is part of the theme issue 'Detecting and attributing the causes of biodiversity change: needs, gaps and solutions'.

Environmental and climate variability drive population size of annual penaeid shrimp in a large lagoonal estuary.

Species with short life spans frequently show a close relationship between population abundance and environmental variation making these organisms potential indicator species of climatic variability. White (Penaeus setiferus), brown (P. aztecus), and pink (P. duorarum) penaeid shrimp typically have an annual life history and are of enormous ecological, cultural, and economic value to the southeastern United States and Gulf of Mexico. Within North Carolina, all three species rely on the Pamlico Sound, a large estuarine system that straddles Cape Hatteras, one of the most significant climate and biogeographic breaks in the world, as a nursery area. These characteristics make penaeid species within the Pamlico Sound a critical species-habitat complex for assessing climate impacts on fisheries. However, a comprehensive analysis of the influence of the environmental conditions that influence penaeid shrimp populations has been lacking in North Carolina. In this study, we used more than 30 years of data from two fishery-independent trawl surveys in the Pamlico Sound to examine the spatial distribution and abundance of adult brown, white, and pink shrimp and the environmental drivers associated with adult shrimp abundance and juvenile brown shrimp recruitment using numerical models. Brown shrimp recruitment models demonstrate that years with higher temperature, salinity, offshore windstress, and North Atlantic Oscillation phase predict increased abundance of juveniles. Additionally, models predicting adult brown, white, and pink shrimp abundance illustrate the importance of winter temperatures, windstress, salinity, the North Atlantic Oscillation index, and the abundance of spawning adult populations from the previous year on shrimp abundance. Our findings show a high degree of variability in shrimp abundance is explained by climate and environmental variation and indicate the importance of understanding these relationships in order to predict the impact of climate variability within ecosystems and develop climate-based adaptive management strategies for marine populations.

Combining fishery data through integrated species distribution models

Abstract Species Distribution Models are pivotal for fisheries management. There has been an increasing number of fishery data sources available, making data integration an attractive way to improve model predictions. A wide range of methods have been applied to integrate different datasets in different disciplines. We focus on the use of Integrated Species Distribution Models (ISDMs) due to their capacity to formally accommodate different types of data and scale proportional gear efficiencies. ISDMs use joint modelling to integrate information from different data sources to improve parameter estimation by fitting shared environmental, temporal and spatial effects. We illustrate this method first using a simulated example, and then apply it to a case study that combines data coming from a fishery-independent trawl survey and a fishery-dependent trammel net observations on Solea solea. We explore the sensitivity of model outputs to several weightings for the commercial data and also compare integrated model results with ensemble modelling to combine population trends in the case study. We obtain similar results but discuss that ensemble modelling requires both response variables and link functions to be the same across models. We conclude by discussing the flexibility and requirements of ISDMs to formally combine different fishery datasets.

Gradients of Variation in the At-Vessel Mortality Rate between Twelve Species of Sharks and Skates Sampled through a Fishery-Independent Trawl Survey in the Asinara Gulf (NW Mediterranean Sea)

Elasmobranchs are priority species for conservation due to their rapid decline determined by the unbalanced struggle between a fragile bio-ecology and strong anthropogenic impacts, such as bycatch from professional fishing. In this context, measuring species resistance to catch of poorly selective gear is of paramount importance. During June-October 2022, five experimental fishing campaigns were carried out in the Asinara Gulf (northern Sardinia) through 35 geographically and bathymetrically representative hauls of an area between 30 and 600 m in depth. Skates prevailed over sharks in the number of species, with seven and five species, respectively. We first evaluated the status of each individual with respect to stress due to the trawl's catch using a three-graded scale. We also recorded individual biometrics (total and disk length, weight and sex, and maturity for males) on board by implementing the best practices in manipulating individuals for physiological recovery and release at sea. After capture, skates resulted in generally better conditions than sharks, although deepwater species of both groups exhibited a worse state than coastal species. The estimated vitality rates also depended on the size of the individuals. This work provides standardized data on the intermingled effect of size, species type, and inhabited depth on the resistance response of some elasmobranch species against capture by trawl fishery activities.

Effects of incomplete sampling and standardization on indices of abundance from a fishery-independent trawl survey off the Atlantic coast of the southeastern United States: Suppl. Fig. 2

Effects of incomplete sampling and standardization on indices of abundance from a fishery-independent trawl survey off the Atlantic coast of the southeastern United States: Suppl. Fig. 2

Effects of incomplete sampling and standardization on indices of abundance from a fishery-independent trawl survey off the Atlantic coast of the southeastern United States

Effects of incomplete sampling and standardization on indices of abundance from a fishery-independent trawl survey off the Atlantic coast of the southeastern United States

Effects of incomplete sampling and standardization on indices of abundance from a fishery-independent trawl survey off the Atlantic coast of the southeastern United States: Suppl. Fig. 3

Effects of incomplete sampling and standardization on indices of abundance from a fishery-independent trawl survey off the Atlantic coast of the southeastern United States: Suppl. Fig. 3

Effects of incomplete sampling and standardization on indices of abundance from a fishery-independent trawl survey off the Atlantic coast of the southeastern United States: Suppl. table

Effects of incomplete sampling and standardization on indices of abundance from a fishery-independent trawl survey off the Atlantic coast of the southeastern United States: Suppl. table

Effects of incomplete sampling and standardization on indices of abundance from a fishery-independent trawl survey off the Atlantic coast of the southeastern United States: Suppl. Fig. 1

Effects of incomplete sampling and standardization on indices of abundance from a fishery-independent trawl survey off the Atlantic coast of the southeastern United States: Suppl. Fig. 1

Considering the influence of land use/land cover on estuarine biotic richness with Bayesian hierarchical models.

The composition of land use/land cover (LULC) in coastal watersheds has many implications for estuarine system ecological function. Land use/land cover can influence allochthonous inputs and can enhance or degrade the physical characteristics of estuaries, which in turn affects estuaries' ability to support local biota. However, these implications for estuaries are often poorly considered when assessing the value of lands for conservation. The focus of research regarding terrestrial and estuarine interfaces often evaluates how LULC may stress estuarine ecosystems, but in this study we sought to understand how LULC may both positively and negatively affect estuaries using measures of observed biotic richness as proxies for estuarine function. We investigated the influence of LULC on estuarine biotic richness with Bayesian hierarchical models using multiple geospatial data sets from 33 estuaries and their associated watersheds along the Gulf of Mexico coastal region of the United States. We designed the hierarchical models with observed species richness of three functional groups (FGs) (i.e., pelagic fishes, forage fishes, and shrimp) from fishery-independent trawl surveys as response variables. We then set salinity and water temperature as trawl-specific covariates and measures of influence from six LULC classes as estuary-specific covariates and allowed the models to vary by estuary, trawl program, salinity, and temperature. The model results indicated that the observed richness of each FG was both positively and negatively associated with different LULC classes, with estuarine wetlands and forested lands demonstrating the strongest positive influences on each FG. The results are generally consistent with past studies, and the modeling framework provides a promising way to systematically quantify LULC linkages with the biotic health of estuaries for the purposes of potentially valuing the estuarine implications of land conservation.

Evidence for spatiotemporal shift in demersal fishery management priority areas in the western Mediterranean

Marine protected areas (MPAs) are a promising management tool for the conservation and recovery of marine ecosystems, as well as fishery management. MPAs are generally established as permanent closures but marine systems are dynamic, which has generated debate in favour of more dynamic designs. As a consequence, the identification of priority areas should assess their persistence in space and time. Here, we develop a step-by-step approach to assess the spatiotemporal dynamics of fishery management priority areas using standard fishery-independent survey data. To do so, we fit Bayesian hierarchical spatiotemporal SDM (species distribution model) models to different commercially important demersal species and use the resulting maps to fit different spatial prioritisation configurations. The proposed method is illustrated through a western Mediterranean case study using fishery-independent trawl survey data on six commercially important species collected over 17 years. We use these results to assess the spatiotemporal dynamics of fishery priority areas. We identified two fishery priority area patterns in the study area, each predominant during a different time period of the study, asserting the importance of regularly reassessing MPA designs.

Spatio-temporal variability in the demersal fish assemblage on the outer continental shelf of the Great Australian Bight

We examined spatial and temporal variations in the demersal fish assemblage on the continental shelf of the central Great Australian Bight to understand how the assemblage is affected by both fishing and environmental gradients. Data from the Great Australian Bight Trawl Sector (1988–2018) and fishery-independent trawl surveys (2005–2009, 2011, 2015, 2018) were used for the analyses. The independent survey data were used to analyse trends in overall species composition and abundances, while the commercial fishery data were used to extend the time series for the key commercial species, Deepwater Flathead (Platycephalus conatus) and Bight Redfish (Centroberyx gerrardi). The demersal fish assemblage was dominated by four commercial species: Deepwater Flathead, Bight Redfish, Ocean Jacket (Nelusetta ayraud), and Latchet (Pterygotrigla polyommata); and one by-catch species: Wide Stingaree (Urolophus expansus). Assemblage composition varied between day/night and along an east-west gradient. Survey abundance and commercial catch-per-unit-effort of several species declined at the end of the time series. Survey abundance was low in 2011, 2015, and 2018 for Bight Redfish and in 2015 and 2018 for Deepwater Flathead. Assemblage composition and catch rates of some species recorded in 2011, 2015, and 2018 were distinct from previous years, but the differences appear to reflect the longer gaps between these surveys and the combined effects of historical fishing pressure and environmental variability. Recent downward trends in the abundance indices of target species, as well as long-term changes in the assemblage, demonstrate the need for continued fishery-independent monitoring. The relative importance of fishing pressure, environmental variability, and other human activities in driving these changes warrant further investigation.

Decline in Atlantic wolffish Anarhichas lupus in the North Sea: Impacts of fishing pressure and climate change.

Anarhichas lupus is a boreo-Arctic species with biological characteristics often associated with vulnerability to overexploitation. Although not commercially targeted in the North Sea, A. lupus is a bycatch species in mixed demersal fisheries. Here we provide an overview of the status of A. lupus in the North Sea, as observed from commercial landings and fishery-independent trawl survey data. A. lupus was once common across much of the central and northern North Sea but, since the 1980s, have declined in abundance, demographic characteristics (reduced size) and geographical range, with the shallower and more southerly parts of its range most impacted. A. lupus is still relatively frequent in the northern North Sea, where fishing intensity, though decreasing, is high. Bycatch through fishing remains a potential threat and, considering the likely impacts of predicted climate change on cold-water species, risks of further regional depletion and/or range contraction remain. Whether or not A. lupus is able to re-establish viable populations in former habitat in UK coastal waters is unknown. Given the lack of data, the precautionary principle would suggest that manageable pressures be minimized where the species and its habitat are at risk of further impacts, and more regular assessments of population status be undertaken.

Quantitative Analysis of the Fishery-Independent Queensland Saucer Scallop (Ylistrum balloti) Trawl Survey

The Queensland saucer scallop Ylistrum balloti fishery is a significant component of the Queensland East Coast Otter Trawl Fishery. In 1996, the saucer scallop stock collapsed, and by 2006, had partially recovered. In 2016, the stock again collapsed, when it was declared, and remains, overfished. In response to the collapses, fishery managers implemented an annual fishery-independent trawl survey of scallop abundance, although funding for the survey has been inconsistent. This study examined 8 y of discontinuous fishery-independent scallop trawl survey data (1997 to 2000, 2017 to 2020). A two-stage approach was introduced to firstly calibrate catch rates for differences between survey vessels for each year, and then derive adjusted mean densities (number ha–1) for the 0+ and 1+ scallop age classes and total scallops, for each year and strata. Quasi-Poisson generalized linear models were used for both stages. Results showed that adjusted mean total scallop densities declined by approximately half from the early survey years (1997 to 2000) to the later survey years (2017 to 2020). Adjusted mean total scallop density and adjusted mean densities of the 0+ and 1+ age classes were lowest in 2020. The 1+ age class numerically dominated survey catch rates.

Sensitivity of marine fish thermal habitat models to fishery data sources.

Statistical models built using different data sources and methods can exhibit conflicting patterns. We used the northern stock of black sea bass (Centropristis striata) as a case study to assess the impacts of using different fisheries data sources and laboratory‐derived physiological metrics in the development of thermal habitat models for marine fishes. We constructed thermal habitat models using generalized additive models (GAMs) based on various fisheries datasets as input, including the NOAA Northeast Fisheries Science Center (NEFSC) bottom trawl surveys, various inshore fisheries‐independent trawl surveys (state waters), NEFSC fisheries‐dependent observer data, and laboratory‐based physiological metrics. We compared each model's GAM response curve and coupled them to historical ocean conditions in the U.S. Northeast Shelf using bias‐corrected ocean temperature output from a regional ocean model. Thermal habitat models based on shelf‐wide data (NEFSC fisheries‐dependent observer data and fisheries‐independent spring and fall surveys) explained the most variation in black sea bass presence/absence data at ~15% deviance explained. Models based on a narrower range of sampled thermal habitat from inshore survey data in the Northeast Area Monitoring and Assessment Program (NEAMAP) and the geographically isolated Long Island Sound data performed poorly. All models had similar lower thermal limits around 8.5℃, but thermal optima, when present, ranged from 16.7 to 24.8℃. The GAMs could reliably predict habitat from years excluded from model training, but due to strong seasonal temperature fluctuations in the region, could not be used to predict habitat in seasons excluded from training. We conclude that survey data source can greatly impact development and interpretation of thermal habitat models for marine fishes. We suggest that model development be based on data sources that sample the widest range of ocean temperature and physical habitat throughout multiple seasons when possible, and encourage thorough consideration of how data gaps may influence model uncertainty.

First Observation of Movement Rates and Repeated Migration in a Western Atlantic Torpedo (Tetronarce occidentalis) in the Northwest Atlantic Ocean

Tetronarce occidentalis (Western Atlantic Torpedo) is a demersal to semi-pelagic batoid, distributed broadly from Nova Scotia to Venezuela, for which data is limited throughout its range. A single individual was captured in the New York Bight and opportunistically tracked through nearshore waters for 2 years using passive acoustic telemetry. The individual showed rapid extensive movements (>250 km) and exhibited continuous use of coastal New York and New Jersey waters during late spring in 2012 and 2013. Observed movements were consistent with captures from fisheries-independent trawl surveys. These observations illustrate that the waters of the Mid-Atlantic Bight may offer important seasonal habitat for Atlantic torpedo rays, providing a preliminary assessment of local movement dynamics.

The influence of environmental factors and fishing effort on demersal fish species in Ghanaian waters

Disentangling the effects of fishing and the environment on fish abundance and distribution is essential for informing future fisheries management measures. Fishery-independent trawl survey data (8 years data between 1999 and 2016) were examined to test influences of fishing effort and environmental variables (temperature, oxygen salinity) on the spatial distribution of two species groups (5 economically important species and 3 non-commercial species) on the continental shelf of Ghana. Fishing effort influenced year-to-year variability in the abundance of 5 species negatively and 2 species positively, with 1 species unaffected. All species showed significant spatio-temporal associations with temperature, salinity and oxygen levels within the region. We observed some interannual consistency in fish spatial distributions given climatic variables’ correlation; however, some variability appeared to reflect tracking of year-to-year shifts in climatic variables, such as inshore–offshore shifts in goatfish, red pandora and red cornetfish associated with thermal and oxygen shifts. While the habitat models did not entirely explain the variability in these spatiotemporal patterns, overall, both commercially targeted and non-targeted demersal species appeared to be impacted by fishing and the species also track spatial and temporal changes in environmental conditions from year-to-year. Future fisheries management regulations in the region should incorporate spatially resolved measures of fishing effort alongside measures of environmental variables.

Predicting the Distribution of Penaeid Shrimp Reveals Linkages Between Estuarine and Offshore Marine Habitats

Marine fish and shrimp species are often dependent on estuarine habitats for juvenile or other early life stages, yet the effect of estuarine habitat availability has rarely been linked to the offshore, marine distribution of species. Penaeid shrimp are an estuary-dependent taxa that have global economic importance and are frequently cited as prey of fish. Species distribution models were developed for three penaeid species in the northern Gulf of Mexico, USA, with the objectives of modeling the distribution of species and testing the influ ence of multiscale predictor variables depicting oceanography, geography, geomorphology, and area of nearby estuaries and coastal wetlands. Fishery-independent trawl survey data of brown shrimp (Penaeus aztecus), white shrimp (Penaeus setiferus), and pink shrimp (Penaeus duorarum) were analyzed with boosted regression tree statistics. Species distribution models of catch per unit effort explained 30–45% of model deviance for brown shrimp and white shrimp; the presence/absence model of pink shrimp had an area under the curve statistic of 0.85 and overall accuracy of 83% correct. Oceanographic predictors had the greatest influence in each of the models, and the spatial distribution of each species was distinct based on these conditions. The marine distribution of all three penaeids was associated with nearby wetland area, and white shrimp were additionally associated with nearby estuary area. Geomorphology predictors were retained less often and were of low relative influence. Our findings demonstrate the importance of considering multiple spatial scales when identifying species-habitat relationships, including the influence of adjacent or nearby environments.