Fisheries Research最新文献

Ariid catfishes (Ariidae family) are important migratory fish species in the Mekong River, with some species representing a major harvest component from the river. Limited biological information exists, and in particular their migration patterns are not well understood. This study examined life history strategies of three abundant ariid catfishes (Cephalocassis borneensis, Arius maculatus, and Osteogeneiosus militaris) in the Mekong River using otolith chemistry. Multiple trace elements in otolith sections were quantified using two analytical techniques: Laser Ablation – Inductively Coupled Plasma – Mass Spectrometry and X-ray fluorescence microscopy. We found that 83 % of C. borneensis samples completed their life cycle exclusively in fresh water in the Mekong River, while 17 % samples of this species were occasionally found in higher salinity (brackish) waters. The two other species (A. maculatus and O. militaris) generally occupied higher salinity (estuary and coastal) areas, but demonstrated complex migratory patterns with up to three migration strategies observed (including both residents and migrants). With such complex migration strategies, management and conservation interventions are a challenge for these fish species.

Identifying and understanding environmental drivers responsible for fluctuations in stock biomass remains a key knowledge gap in data limited commercial crustacean fisheries such as the brown crab Cancer pagurus. This study investigated the use of historic beam trawl data as a fishery independent density index and its relationship with fishery dependent data. The role of the North Atlantic Oscillation (NAO), a key latent predictor, and other environmental drivers (brooding temperature, larval development temperature and phytoplankton density) on density of C. pagurus in the North West Irish Sea was also investigated. The identification of a significant relationship between fisheries dependent and independent data demonstrates the role of fisheries independent survey data to monitor changes in density in C. pagurus populations. Lagged NAO, brooding temperature and larval temperatures had significant effects on C. pagurus density, with negative NAO phases and increasing brooding and larvaal temperatures resulting in increased C. pagurus density. The significance of these relationships is explored in the context of our understanding of relative stock status and future sustainable fisheries management for C. pagurus in the North East Atlantic.

Patagonian toothfish (Dissostichus eleginoides) supports valuable fisheries across the Southern Ocean under the management of the Commission for the Conservation of Antarctic Marine Living Resources. The fishery at South Georgia accounts for 26 % of the catch of this species in the Southern Ocean in the last 25 years. This study assesses the effects of exploitation and changes in management of the fishery on long-term trends in biological traits of Patagonian toothfish at South Georgia. Our results show variability in the size of fish, but no evidence of a systematic decline during the 25-year period. The mean size of fish was linked to recruitment, with pulses of recruitment associated with a reduction in mean size of the fishery. The years when recruitment was highest were in 2000–2010, with >50 % of toothfish of length classes < 90 cm. Management measures implemented over the last 25 years, including depth restrictions and benthic closed areas, have resulted in a gradual stabilization of the population structure. Catch per unit effort (CPUE) dropped from 1997 to 2010, gradually increased until 2017 and since 2018 has returned to values typical of the mid-2010s. Monthly changes in fish length, depth of capture and CPUE confirm that the spawning peak is in July. Size at maturity has remained stable over the last 25 years, suggesting the fishery has not had a major impact on population size structure. These results illustrate the role of management regulations in limiting the impacts of commercial exploitation on the population structure of a long-lived fish species. Given the bigger-deeper size pattern in Patagonian toothfish, there may be a case for increasing the minimum depth of the fishery (currently 700 m) when strong recruitment pulses are detected.

Gray triggerfish (Balistes capriscus) historically have been aged by counting translucent zones in thin sections prepared from their first dorsal spine because their small, fragile sagittal otoliths are difficult to extract and process for ageing. However, recent research suggests dorsal spine translucent zone counts produce biased age estimates, thus the historical dorsal spine-based ageing protocol results in a systematic underestimation of true age. Here, we employed the bomb radiocarbon chronometer to test the accuracy of age estimates (n = 3 readers) derived from opaque zone counts in whole otoliths, as well as dorsal spine section translucent zone counts produced with the historical ageing protocol and a new method that requires higher magnification to count translucent zones on the margin of dorsal spine sections. Results indicate historical dorsal spine-derived age estimates underestimate age, with the extent of bias increasing with age. There was no evidence of ageing bias for both whole-otolith opaque zone counts and new protocol dorsal spine translucent zone counts. New dorsal spine protocol ageing was slightly more precise among readers (iAPE = 9.4 %) than otolith ageing (iAPE = 10.1 %) and read times were 2–3x faster for dorsal spine sections than whole otoliths. Validation of the new dorsal spine ageing protocol is a critical step in effective production ageing of gray triggerfish. Archived dorsal spine sections can be re-aged with the new protocol to update historical age composition data, and future ageing will not have to rely on the logistically challenging extraction and processing of otoliths.

This paper reviews the recent progress in the application of Lagrangian methods for detecting potential feeding and fishing grounds and the relationship between the dynamic features with strong gradients of the relevant indicators of water motion, Lagrangian fronts (LFs), and catches of different species of pelagic fish and squid. The locations of the LFs, approximating locations of the ocean features with increased values of the gradients of hydrological parameters, can be calculated by solving advection equations for a large number of virtual passive particles in the altimetric velocity field or in the velocity fields generated by numerical circulation models or obtained using high-frequency radars. The LFs can be easily identified in the near real time, under any weather conditions and in the areas with small contrasts of sea surface temperature. The proximity of catch sites to location of LFs has been shown with the help of statistical tests in different seas and oceans based on catch reports of fishing vessels. The active and passive physical mechanisms at fronts, that may provide favorable conditions for foraging and feeding, are discussed. The paper emphasizes the importance of fronts in marine ecology and sustainable fisheries.

Small-scale fishing, characterised by small groups of people working with basic technology and little investment, is an important economic activity in regional and global contexts. In Latin America, inland fisheries play a very important socio-economic role, providing food and income to local families, alleviating poverty, and contributing to social well-being. They are often structured as a social cooperative, as a way to ensure productivity. Cooperatives tend to be sustainable, and their performance can be judged from the impact they have on the social, economic, and environmental spheres. The aim of this study was to measure the sustainability of inland fishing cooperatives in Mexico from these three viewpoints. Though cooperatives generally show a medium-high level of sustainability, on account of their historical background and their contribution to social and economic indicators, our results revealed some weaknesses in terms of environmental indicators, which are locked in a negative relationship with economic ones. Social indicators, however, were positively related with the other two. The sustainability of fishing cooperatives today faces various challenges, as political decision-making tends to favour the social and economic dimensions over the environmental one.

Since winter 2016, an increase in strandings of small cetaceans has been recorded along the French Atlantic seaboard. This mortality, which concerns mostly the short-beaked common dolphin (Delphinus delphis), is mainly due to bycatch in fishing gears. Highly vulnerable towards this issue, this protected species is more and more threatened in the Bay of Biscay. Fine scale knowledge on fisheries practices, which are ever evolving, is paramount to address the bycatch issue. The objective of this study was to identify the individual trajectories of static netters flying the French flag and to highlight possible changes in their practices between 2015 and 2019, during the winter period. An analysis of AIS data from vessels over 15 m of length, using a clustering method (HCPC), enabled us to define a typology of the static net fishery trajectories. The possible main trajectories of static netters flying the French flag were identified. Among these, one trajectory was linear with a constant navigation path and was used by offshore gillnetters targeting hake. This trajectory increased in frequency between 2015 and 2017. This study improves knowledge on practices of passive fishing gears that present a risk of short-beaked common dolphin bycatch such as gillnets and trammel nets in the Bay of Biscay. Further analysis of AIS data from other years and fishing fleets, adding environmental data or even dolphin distribution, are needed for a full understanding of the bycatch issue and towards the implementation of efficient mitigation measures.

The American lobster, Homarus americanus H. Milne-Edwards, 1837 supports a valuable fishery subject to rapid warming of the Gulf of Maine (GOM) and Georges Bank (GBK). Comprehensive information related to large-scale larval distribution is lacking due to the logistical challenge of sampling their hyper-dispersed larvae. In 2021, we established seasonal abundance patterns of larvae and their prey in the GOM on an unprecedented spatial scale with a season-long survey at transects spanning approximately 300 km of coastline. We compared the current distribution of larvae with historical surveys with respect to differences between inshore and offshore (5 versus 40 km), and between eastern and western hydrographic regions. We also examined spatial and temporal patterns in the abundance of zooplankton prey. The distribution of recently hatched stage I larvae extended offshore at the transect off Rye, NH and was consistent with the reported movement of ovigerous lobsters offshore to hatch their eggs. By contrast, stage I larvae were most abundant nearshore and rare offshore at other transects along the coast. Our results confirmed historical patterns of high abundance of competent stage IV larvae in the western Gulf of Maine and low abundance in the east. We also identified the potential for a temporal mismatch between the abundance of larvae and the biovolume of copepods at transects in Milbridge, ME and Rye, NH with peak copepod abundance occurring either well before or after the peak abundance of lobster larvae. The data collected fill a gap in our understanding of larval distributions and seasonal progression in the Gulf of Maine, establish a baseline for future studies, and provide an opportunity to validate established biophysical models of larval transport. Yet a longer time series of broad-scale surveys is needed to better understand intricacies of factors influencing larval abundance and distribution. The project was an industry-led collaboration with government and academic scientists providing proof of concept for future collaborative research.

Fish condition is often defined as a deviation in the relationship between fish weight and length, indicating if the fish is leaner or fatter than the average. The proportion of a stock in critically poor condition may indicate a component of the total natural mortality rate M, which has been called the starvation mortality rate (i.e., M_K ≤ M). The weight-length relationship may vary spatially and temporally (both between and within years). Hence, M_K may also vary the same way. We developed a spatiotemporal condition model to derive a spatiotemporal and length-specific index of M_K. We aggregated M_K across space and months to produce an annual and length-specific M_K index for the entire stock, as a potential input to assessment models. We applied the model to survey data for cod on the Southern Grand Bank of Newfoundland. Our results indicated that M_K was: 1) higher in the spring than the fall, 2) higher for cod between 55 and 80 cm and cod ≥ 120 cm, and 3) higher during 1991–1993 when the stock declined substantially, but was also high in 2016. We discuss potential drivers of starvation mortality as well as how this information can be included in a stock assessment model to improve fisheries management advice.

Recent declines in American lobster (Homarus americanus) settlement in the Gulf of Maine (GoM) have raised questions concerning the effects of climate change on lobster recruitment. Postlarval lobsters are strong swimmers that typically transit to inshore settlement habitats, an energy-intensive process that may be a metabolic bottleneck. Using 72-hr laboratory swimming challenges, we tested the performance of laboratory-reared postlarvae at historically favorable temperatures (15°C), as well as projected end-of-century GoM temperatures (22°C) to determine if increased water temperatures may impair the swimming abilities needed to reach settlement habitats. Video observation and analysis revealed that postlarvae in the 22°C treatment spent 25 % less time actively swimming compared with postlarvae at 15°C. Postlarvae in the 22°C swimming trials also had lower lipid content after the swimming challenge when compared with pre-trial controls; however, dry weight and protein content were not significantly different between the treatment groups. When sequential trials were run using postlarvae from the same clutch, dry weights increased with time since metamorphosis. Metabolic rates for lobsters increase in warmer temperatures, so it is possible that decreased swimming at warmer temperatures may be an adaptive strategy for energy conservation in less favorable, thermally stressful, conditions. Overall, decreased swimming activity in warmer waters may be a contributing factor in shifting patterns of lobster recruitment in the GoM.