Fisheries Management and Ecology最新文献

Despite the global importance of inland fisheries, data available for stock assessment is often limited. Data-limited methods that use length composition data offer a potential approach to assessing more inland fisheries. We assessed the population status of three fish species in Lake Hovsgol, Mongolia through length-based spawning potential ratio (LBSPR) analysis and evaluation of trends in eight length-based indicators of population status, catch-per-unit-effort (CPUE), and body size. Hovsgol grayling (Thymallus nigrescens) were not yet overfished, but CPUE and body size declined due to targeting of large, mature fish. Lenok (Brachymystax lenok) were experiencing overfishing, especially of small, immature fish, which contributed to size–structure truncation. The burbot (Lota lota) population was healthy according to most indicators, but the lack of local life history information exacerbated already large uncertainties. Continued monitoring and improved coordination among fishers, managers, and scientists will be critical to enhancing the sustainability of these fisheries.

Fish communities on artificial reefs have rarely been monitored over long periods to evaluate success of reef deployment. Here, we used roving diver surveys to assess changes in fish assemblages on a large, reefed vessel during 2008–2017. Multivariate analyses revealed a dynamic community that stabilized after 5 years. Species richness increased and species dominance decreased during 2008–2017. The fish community shifted toward reef-associated species such as hogfish and pufferfish. Species composition shifted, but trophic structure was relatively stable, which suggested that functional groups may not reflect larger community shifts. Our results indicate that fish communities on artificial reefs are temporally dynamic and that long-term monitoring is needed to understand how fish assemblage structure changes through time.

Vulnerable marine ecosystems (VMEs) are typically fragile and slow to recover, thereby making them susceptible to disturbance, including fishing. In the high seas, the United Nations General Assembly (UNGA) requested regional fishery management organisations (RFMOs) to implement measures to prevent significant adverse impacts on VMEs. Here, we predict spatial abundances of 15 taxa, 13 VME indicator taxa, in the South Pacific RFMO (SPRFMO) area. Models used seafloor imagery data, an important advance on previously developed presence-only predictions, to provide information on spatial variation in taxa abundance that is crucial for better inferring likely location of VMEs, rather than just distribution of VME indicator taxa. Abundance models varied in predictive power (mean R² ranged 0.02–0.40). Uncertainty estimates of model predictions were developed to inform future spatial planning processes for conservation and management of VMEs. Using the VME index concept, abundance model outputs and previously published presence-only model predictions were weighted using vulnerability scores, to explore how modelled outputs could provide spatial estimates of likely VME distribution. Spatial predictions of abundance improved on previous modelling to provide an almost complete suite of abundance models for VME indicator taxa in the western portion of the SPRFMO Convention area. Nevertheless, to improve utility of modelled outputs, we recommend more high-quality seafloor imagery data be gathered within the SPRFMO Convention area to (1) validate abundance models developed here with independent data from the model area, (2) update models, if necessary, (3) link abundance information to ecosystem function and (4) explore validity of the adapted VME index approach used here.

Recreational fishing surveys have an important role in providing data to inform fisheries management. The selection of a contact method is an important and often challenging consideration that influences the potential for non-sampling errors that can result in unrepresentative data and biased estimates. Telephones are used for many off-site recreational fishing surveys, but widespread use of digital technology suggests that online surveys could be a viable alternative. We compared phone surveys with alternative online surveys using probability sampling from a licence database. Response rates were lower for online surveys (13%–26%) than phone surveys (97%–98%). The proportion of respondents who reported marine fishing in the previous 12 months did not differ between survey methods (98% for both survey modes), but the proportion of avid fishers was higher for online surveys (41%–54%) than phone surveys (37%–40%). These differences reflect higher respondent burden for online surveys where data are self-administered and respondents are more likely to opt-out. Higher non-response and over-representation of avid fishers from online surveys may compromise data reliability. We recommend comparative studies to quantify and correct for biases when evaluating alternative survey modes for new or ongoing surveys.

Regional factors correlated with recruitment of black bass (largemouth bass; Micropterus nigricans and smallmouth bass; Micropterus dolomieu), two important fishes, are rarely studied, despite the importance of recruitment variation in influencing fish populations. We sought to identify factors that drove variation in age-0 and age-1 black bass abundance. Age-0 or age-1 black bass catch per unit effort (CPUE) in reservoirs in Kansas and Illinois, USA, was positively correlated with local short-term (i.e., mean April precipitation) environmental variables. In contrast, age-0 or age-1 black bass CPUE was generally negatively correlated with long-term environmental variables and river regulation metrics (i.e., reservoir elevation) in the Mississippi and Missouri river reservoirs. Our findings highlight that consideration of spatiotemporal scale is important when managing black bass populations.

Biological invasions pose a serious threat to native biodiversity, and climate change intensifies the risk of non-native species invasion in human-altered environments, particularly in freshwater ecosystems. In South Korean freshwaters, the number of non-native fish species increased significantly since the early 1950s. We screened risk of invasion by 43 freshwater fish species in South Korea using the Aquatic Species Invasiveness Screening Kit (AS-ISK). Of these species, 26 (~ 61%) posed a high to very high risk of invasiveness. Black bullhead Ameiurus melas, brown bullhead Ameiurus nebulosus, North African catfish Clarias gariepinus, green sunfish Lepomis cyanellus, black carp Mylopharyngodon piceus, round goby Neogobius melanostomus, and Chinese sleeper Perccottus glenii were very high risk under current and predicted climate conditions. Striped snakehead Channa striata, longear sunfish Lepomis megalotis, smallmouth bass Micropterus dolomieu, white perch Morone americana, Eurasian perch Perca fluviatilis, and rudd Scardinius erythrophthalmus were high risk only under predicted climate conditions. Present risks were generally consistent with previous qualitative assessment, with some discrepancies, likely due to unobserved or under-reported invasive traits of some species or a better ability of the present semi-quantitative approach to estimate potential risks. Our results will inform South Korean decision-making to potentially enhance regional cooperation across East Asia against transboundary introductions of aquatic invasive species.

Accuracy of catch landing data reported by captains of commercial vessels is crucial in the assessment of marine species stocks and in fisheries policy and management. However, this data can be subject to estimation biases, such as a tendency to inflate some catches (to the detriment of others) and refusal to fill in logbooks. We assessed the accuracy of catch reports from the Spanish tropical tuna purse seine fleet (which accounts for 26% of catches in the Indian Ocean) using Benford's law, a mathematical principle effective for detecting irregularities across multiple datasets. During 2013–2020, including periods before and after the implementation of total allowable catch (TAC) limits in 2017, reported catches differed from Benford's expected distribution, especially for bigeye tuna, indicating potential inaccuracies in reported catches. Changes in data reporting after TAC limits were imposed in 2017 suggested modifications in fishing operations and reporting practices. Use of Benford's law highlighted its potential as an auditing tool in fisheries management and provided insights into data integrity that are crucial for sustainable fisheries governance.