Fisheries Management and Ecology最新文献

The stock assessment model for the Antarctic krill fishery is a population model operating on daily timesteps, which permits modeling within-year patterns of some population dynamics. We explored the effects of including within-year patterns in natural and fishing mortality on catch limits of krill, by incorporating temporal presence of key predator species and contemporary temporal trends of the fishing fleet. We found that inclusion of within-year variation in natural and fishing mortalities increased catch limits. Fishing mortality had a greater effect than natural mortality despite differences in top-down predation on krill, and potentially increased catch limits by 24% compared to the baseline model. Additionally, the stock assessment model allowed a higher catch limit when fishing was during peak summer months than autumn. Number of days with active fishing was negatively related to precautionary catch limits. Future stock assessments should incorporate contemporary spatiotemporal fishing trends and consider implementing additional ecosystem components into the model.

Marine protected areas (MPAs) are globally recognised for their role in safeguarding marine fisheries from the detrimental impacts of human activities and climate change. Tanzania, in alignment with global conservation efforts, has designated 18 MPAs and plans to establish four more in the Southwestern Indian Ocean. However, a critical challenge arises from the lack of a thorough understanding of genetic connectivity between populations in MPAs and non-protected areas (NPAs). To address this, 151 mitochondrial D-loop sequences (357 base pairs) of Barred mudskipper (Periophthalmus argentilineatus) were analysed to assess genetic connectivity between MPAs and NPAs in Tanzania. The findings revealed a low and insignificant index of genetic differentiation (F_ST = −0.0046, p > 0.05) between populations in MPAs and NPAs. Furthermore, haplotypes from both MPAs and NPAs did not cluster based on their geographical origins, with over 9 haplotypes shared between these areas. Additionally, the measured haplotype and nucleotide diversities did not differ significantly between MPAs and NPAs (p > 0.05). However, MPAs showed a significantly higher number of private haplotypes compared to NPAs (p < 0.05). These findings suggest high genetic interconnectedness between populations in MPAs and NPAs, underlining the importance of existing MPAs in preserving local genetic diversity and their potential to replenish depleted NPAs. However, realising the full potential of this interconnectedness necessitates stringent enforcement of sustainable fishing practices to alleviate pressure on fish stocks. It also requires the protection of critical habitats that serve as corridors for fish dispersal, facilitating interconnectedness between MPAs and NPAs.

Few studies have acknowledged and quantified the economic contribution in expenditures of recreational fisheries. Additional economic value attributed to fishers' willingness to pay (WTP) for recreational fisheries in excess of expenses was estimated for 33 countries in Europe. Benefit transfer was used in a meta-regression analysis of 184 studies and 1001 observations of WTP per day for recreational fisheries. Most studies of fishing were in the USA, but also in Europe, Australia, New Zealand, South America and Canada. Mixed-effects regression models were estimated with income, climate variables, population density and study characteristics as explanatory variables. Income and temperature positively affected WTP per day. Benefit transfers with these variables and different transfer methods among European countries showed that the estimated total WTP could amount to 11.4 billion USD (purchasing power parity corrected to 2020 prices). Variation in WTP per day was large, and ranged 9–62 USD among countries and transfer methods. For several countries, WTP for recreational fisheries exceeded 0.1% of gross domestic product.

The age-structured assessment model available in the MSEtool R package assesses stock status and exploitation for varying data availability, from limited to rich datasets. We investigated model accuracy in relation to data availability, population exploitation levels, initial population assumption and fishery selectivity misspecification. Estimates were accurate in all conditions when data were available for a stock in an unfished state. However, for estimates to be accurate without complete exploitation data, total catch and abundance index data needed to span more than two stock generations. When the data time series was shorter than two generations, fishery mean lengths spanning one generation improved relative estimates (e.g. depletion), but precise estimates of unfished recruitment required fishery age- or length-structured data.

We analyzed three-dimensional (3-D) spatial and temporal variation of biomass density associated with drifting fish aggregating devices (dFADs) in the western and central Pacific Ocean. Detection depth of dFAD echosounder buoys was divided into three layers, for estimation of biomass density in each layer based on detected water volume. Temporal variation and spatial distribution of biomass density in each layer were compared. Similarity of biomass density gravity center shifts in each layer were assessed using the dynamic time warping (DTW) regularization algorithm. Biomass density varied regularly over ~1 month, with the 2nd and 3rd layers delayed ~14 days compared to the 1st layer. Biomass distribution range and density values were higher in the 1st layer than the 2nd and 3rd layers, but locations of maximum biomass density were close. The distribution of biomass density gravity centers between adjacent water layers were similar, with gravity centers of the 2nd and 3rd layers shifted over time in relationd to the 1st layer. Our study demonstrated that the aggregation behavior of species from different water layers attracted by dFADs were related, and emphasized the necessity for ecosystem-based fisheries management.

Unprecedented warm river temperatures in July 2023 in Labrador, a subarctic region of Canada, were the highest since monitoring began (1994–2023) and ranged from 19.4°C (Hunt River) to 22.5°C (Eagle River). Incipient lethal water temperatures were exceeded for adult Atlantic salmon and brook trout (≥25°C) on 14 days in five of seven rivers and Arctic charr (≥24°C) on 17 days in six of seven rivers. Consequently, Labrador had the greatest number of angling restrictions and closures in 2023. Recent warming serves as a warning to fishery managers of regions historically unaffected by heat waves of the need to prepare action plans that mitigate the effects of a warming climate on fishes.

The Queenfish, Scomberoides commersonnianus, is a large commercial fish in Bangladesh. This is the first study on the Queenfish that aims to elucidate life history parameters and stock status to suggest authority for sustainable management and to support future research on this economically significant species in the region. We used three length-based approaches to establish a standard for sustainable management of the fishery: (1) TropFishR to give the growth parameters and current exploitation status, (2) the length-based Bayesian biomass estimation (LBB) to quantify stock biomass, (3) and Froese's sustainability indicators (LBI). The length–weight relationship of Queenfish was a negative allometric pattern (b = 2.84; R² = 0.98). Growth parameters for Queenfish were L_∞ = 124.22 cm, K = 0.31 year⁻¹. Instantaneous total mortality Z = 0.71 year⁻¹, instantaneous natural mortality M = 0.36 year⁻¹, and instantaneous fishing mortality F = 0.35 year⁻¹. Based on the LBB approach, the current estimated stock biomass was overexploited (B/B_MSY = 0.65). We recommend strictly maintaining mesh size of nets to reduce harvest of immature fish shorter than 62 cm, while focusing harvest on fish 62–74 cm, to minimise recruitment and growth overfishing.

Acoustic telemetry (AT) has emerged as a valuable tool for monitoring aquatic animals in both European inland and marine waters over the past two decades. The European Tracking Network (ETN) initiative has played a pivotal role in promoting collaboration among AT researchers in Europe and has led to a significant increase in the number of tagged and observed aquatic animals in transboundary European waters. While AT benefits decision-making and delivers essential data to management bodies, its potential for management decision-making mechanisms has yet to be fully harnessed. We reviewed existing research, studies, and organisational initiatives related to aquatic animal tracking and their utility in fisheries management in European waters. We found that AT has already contributed to many aspects of fisheries management, such as improved understanding of stock dynamics, identification of critical habitats, assessment of migration routes, and evaluation of the effectiveness of conservation measures. However, broader utilisation of tracking technologies is needed. By leveraging the full potential of AT, managers can make more informed decisions to protect, restore, and sustainably manage European waters and creatures that live therein.

Transboundary freshwater fish are critical for both biodiversity and community well-being but face alarming overexploitation in shared rivers. Such rivers greatly aid the livelihood and nutrition of local people on both sides of shared borders. However, a lack of understanding of resource dynamics and utilization patterns hinders sustainable management of resources. We investigated spatiotemporal fish assemblages along the River Atrai, a transboundary river between India and Bangladesh. The socioeconomic status of fishers was quantified from personal interviews and group discussions to estimate the exploitation trajectory of piscine resources. Fish assemblages varied significantly among locations and seasons. Species diversity was highest downstream and lowest upstream. Spatiotemporal fishery exploitation aligned with fish diversity among sites and seasons, with fishers preferring to fish in downstream areas during the post-monsoon season. Fishers were economically weak, with limited sources of income. Therefore, adequate integrated management plans should be implemented to ensure resource resilience in a transboundary pocket, sustainably supporting the livelihood of concomitant fishers.