Fisheries Research最新文献

We conducted a Productivity Susceptibility Analysis (PSA) to empirically assess the vulnerability risk of marine ornamental reef fish in Sri Lanka for exploitation. We considered distribution, accessibility, ecological niche, and market price as susceptibility attributes, while fecundity, larval development, maximum length, and longevity were productivity attributes. The vulnerability score, demand, and market price were used to assess species prioritization, and then compositions of the prioritized species were computed. The veracity of primary and secondary data collected on susceptibility and productivity attributes was confirmed by interviewing traditional fishers in situ. The IUCN and present PSA classifications for the medium susceptibility risk species were comparatively assessed. Four species out of 17 medium susceptibility risk species were encountered as the medium vulnerability risk species for exploitation. The Pacific cleaner shrimp (Lysmata amboinensis) emerged as the highest prioritized species. In addition, we observed significant differences in the species’ status assessed through the PSA approach compared to the IUCN status. The study affirms that demand and market prices substantially influence the exploitation vulnerability of species, and the PSA offers a promising multidisciplinary approach to evaluating intrinsic and extrinsic factors in conservation ecology compared to widely used IUCN status for assessing extinction risk. Furthermore, the present findings have practical implications, as they warrant essential policy changes for conserving the prioritized species and the medium vulnerability risk species encountered in the present research to extinction risk.

The European catfish (Silurus glanis) is a large apex predator native to Eastern Europe. Increasing populations within and outside the species’ native range in recent years, and its popularity with recreational anglers are fueling discussions about appropriate management. To understand the motivations of anglers and their views on different management strategies, an internet survey was conducted in southern Germany. The results showed that catfish anglers differ in several aspects from those targeting other species. For specialists, catfish fishing is a central part of life, and they invest significant time and money to catch trophy sized fish. Most catfish anglers think that their targeted species has no negative effect on the local fish community and practice catch and release, despite this practice being illegal in Germany. Large catfish are often released under the misapprehension that they are inedible. The findings of this study suggest that new fishery management approaches are needed in order to mitigate the impact of European catfish in southern Germany. A co-production approach actively incorporating anglers’ perspectives will be essential in implementing education and incentives for catfish consumption alongside other aspects of fisheries management.

Caribbean spiny lobsters are known to undergo migration as adults, but the dispersal and homing ability of subadults and juveniles is not well characterized. Given that settlement habitat for juveniles is inshore seagrass / hardbottom and reproductive habitat is offshore coral reefs, dispersal during ontogeny serves as a bottleneck potentially limiting adult population density. Previous studies have examined factors associated with movement and den selection by juvenile lobsters such as shelter type, predators, and conspecific density. Their attraction to odors of healthy conspecifics plays a significant role in aggregation of lobsters in casitas and traps. But what is unknown is whether juvenile lobsters possess the map and compass orientation found in adults. To examine the ontogeny of homing ability, we conducted multiple mark / displace tracking studies using acoustic telemetry in juvenile hardbottom and subadult coral patch reef habitats. All lobsters regardless of size tend to relocate to new crevice shelters when handled, even if returned to their original shelter. Thus, for non-displaced lobsters tagged and returned to their point of capture, distance and angle travelled appears to be random with distance increasing as function of body size. However, for juvenile and subadult lobsters tagged and displaced away from their point of capture, the distance and angle travelled when released is significantly directed toward the point of capture. Thus, it appears that the map and compass ability of Caribbean spiny lobsters appears early in ontogeny and may allow for individuals to safely explore unfamiliar locations while retaining knowledge of how to return to known shelter. This ability to expand their known habitat map while maintaining knowledge of critical diurnal shelter locations is expected to facilitate their ontogenetic dispersal to adult habitat.

We performed a study on standardizing the catch per unit effort (CPUE) for blue endeavour prawns (Metapenaeus endeavouri) caught in the Northern Prawn Fishery (NPF), one of Australia’s largest and most valuable prawn fisheries. Blue endeavour prawns constitute a significant proportion of the total NPF catches. However, there have been very limited studies on their population dynamics. This study assessed the effectiveness of Artificial Neural Networks (ANNs) for CPUE standardization, with a focus on blue endeavour prawns as a case study. Our approach involved developing new ANN models for CPUE standardization with two key ideas: using an architecture inspired by the catch equation to mitigate overfitting; and using the Tweedie distribution to manage uncertainties and zero counts in the catch data. Specifically, we grouped variables into three distinct modules based on the catch equation, with each representing catchability, fishing effort, and fish density, respectively. Parameter estimation for our ANNs was achieved by maximizing the likelihood using a coordinate descent approach, which alternates between optimizing the Tweedie distribution parameters (power and dispersion) and the standard neural net parameters. We conducted a comprehensive comparison among ANNs, generalized linear models, and generalized additive models. The findings suggest that customizing ANN structure improves model fitting and effectively mitigates the risk of overfitting. It also reveals a promising path for the application of neural networks in CPUE standardization.

The Caribbean spiny lobster (Panulirus argus) fishery in Florida, valued at millions of dollars annually, relies mostly on wooden-slat traps baited with live, sublegal-size lobsters to attract legal-size individuals. However, this practice leads to confinement-related mortality due to starvation and depredation. We investigated the escape rates and mortality of bait lobsters using long-term deployable cameras, documenting behavior of bait lobsters in traps. Although previous research found that long-term confinement of these bait lobsters results in their poor health and mortality, these estimates of mortality relied on periodic observations of traps that could not differentiate causes and timing of mortality. To identify how the long-term confinement of bait lobsters affects their likelihood for escape or mortality, we deployed traps with one lobster for each of the following treatments: healthy/fed or starved for 2, 4, or 6 weeks. Long-term deployable cameras and infrared lights mounted on traps were used to observe the fate (i.e., escape or mortality) of these lobsters over a 2-week trap soak period typical in the fishery. We conducted 12 deployments of 103 total traps over 1 year and found that escape varied with duration of lobster starvation. Our study confirmed escape rates from past studies (1.26 ± 0.43 % of lobsters per day) and revealed "serial confinement," where escaped lobsters re-entered traps, potentially prolonging their confinement and mortality risk. Starvation, caused by long-term confinement, resulted in increased mortality, with smaller lobsters (<68 mm carapace length) facing higher risk of mortality. Video documentation allowed for the first time to differentiate between starvation mortality and depredation within traps; depredation by octopuses (Octopus briareus) and triggerfish (Ballistes spp.) posed a substantial threat, reducing trap catch efficiency. Our video documentation showed that the presence of dead lobsters in traps further decreased catch rates for the duration (∼5d) the carcass remained in the trap, underscoring the negative impact on fishery yield. Our findings emphasize the need for the fishery to explore management strategies to mitigate mortality of sublegal-size lobsters in traps due to long-term confinement, including trap reduction, use of escape gaps, and shorter trap soak times, akin to successful practices in other spiny lobster fisheries. The study highlights the utility of long-term deployable cameras in assessing trap functioning and catch dynamics, offering insights for sustainable management of Florida's lobster fishery while preserving its cultural and economic significance.

Indonesia is one of the sea cucumber-producing countries with small-scale fisheries activities in harvesting multi-species products. Few biological data are available for sea cucumber fished from the Indonesian sea floor. This study assessed species diversity and compiled a great amount of biometric data on commercial sea cucumber species observed from 23 locations representing east to west Indonesia, focusing on the intertidal habitats covering seagrass and coral reefs. A total of 4553 individuals of sea cucumbers belonging to 39 commercially valuable species were observed; size composition, length-weight relationships, and Fulton’s condition factors were investigated. The assessment demonstrated that only several species were observed in large sizes. The current study added Holothuria flavomaculata and H. verrucosa to the list of exploited species nationally; therefore, 55 sea cucumber species have been confirmed under commercial harvest in Indonesia. Holothuria albiventer, H. excellens, H. flavomaculata, H. rigida, H. verrucosa, and Stichopus quadrifasciatus are discovered as newly reported species being fished for trade globally that have not yet been included in the FAO commercially important sea cucumber list. The body size frequency distributions show that most animals observed in the field during the study period were generally small; this may indicate that sea cucumber populations in Indonesia are under serious exploitation because exploited populations tend to have lower frequencies in larger classes. This is the first study to calculate the length-weight relationships of four species (Holothuria fuscocinerea, H. hilla, H. impatiens, and Stichopus vastus). Thus, the length-weight relationships of nine species in Indonesia have been investigated. Eight species analyzed in this study grow allometrically with a negative allometric. Fulton’s coefficient condition factor displayed that almost all species in nearly all locations had high values, which indicates that local environmental conditions are favorable and support the physical health of the sea cucumbers. This current study provides novel data and will be beneficial in estimating weight in future fishery surveys to estimate stock biomass and catch volumes. It can also be used by the Indonesian scientific authority to recommend the wild catch size of the species involved in the trade to the management authority.

Assessing the efficiency of fishing gears, i.e. the fraction of fish in the gear path that are caught and retained, is essential for providing reliable abundance estimates in the management of sedentary invertebrate fisheries. While various methods have been proposed for estimating gear efficiency from experiments, each approach has its strengths and weaknesses, influenced by factors such as resource distribution, tow overlap, and positional errors. In this study, we conducted simulations to gauge the accuracy and precision of four different methods commonly used for estimating gear efficiency and initial density in depletion experiments: Leslie-Davis, DeLury, Removal, and Patch; considering different spatial arrangements of resources, degrees of tow overlap, and positional inaccuracies. We followed designs used in depletion experiments conducted in the Patagonian scallop fishery, commonly employed in scallops and other sedentary species’ fisheries. Our findings reveal that the Patch model, which is specifically harnessed to account for the spatial impact of tows, outperforms the others in terms of accuracy and precision, provided there is no positional error. Estimation of initial density in the simulated depletion experiments showed a similar pattern than that for gear efficiency. The spatial distribution of scallops had no noticeable effect on the precision and bias of efficiency and intial density estimates for any of the models. This holds across all scenarios of spatial clustering and tow overlap. However, when high positional errors in tow locations are at play, the Patch model’s performance is comparable to the other methods. The study highlights the advantages of the Patch model, especially in light of the current availability of high-precision GPS systems that can accurately track tow locations. We also discuss why traditional models may be less suitable for sedentary benthic species, underscoring the importance of selecting appropriate methodologies for specific fishery management tasks.

Seasonal harvest restrictions are a common strategy in fisheries management, designed to mitigate fishing pressure on economically and recreationally valuable fish and invertebrate stocks. However, uncertainty regarding recreational fishing effort responses to seasonal closures can lead to unintended consequences for target and non-target species. This is especially true in the Gulf of Mexico reef fishery, where anglers can switch among multiple target species and discard mortality for co-occurring species is high. Therefore, understanding the drivers of recreational fishing effort is needed to support management decisions. This study addresses knowledge gaps by employing a statistical model to analyze the relationships between recreational reef fish effort (measured in angler-trips) and species-specific seasonal management in the Gulf of Mexico along the west coast of Florida. We focused on ecological and management variables surrounding gag (M. microlepis), red grouper (E. morio), and red snapper (L. campechanus), which are among the most recreationally sought-after species targeted along the west coast of Florida. We also considered environmental covariates such as seasonal patterns, inter-annual changes in species abundance, and socioeconomic factors (i.e., numbers of saltwater fishing licenses sold and economic trends). Our analysis indicated considerable variation in effects of seasonal, environmental, and management predictors on recreational effort that were region-specific. Notably, management predictors related to both red snapper and gag, such as the fraction of a month open to harvest (both species) and the length of the red snapper season, directly influenced recreational effort. Given recent substantial reductions in the Gulf of Mexico gag season, we were particularly interested in the effect of gag management on angler-trips, but we did not find strong evidence that effort concentration has taken place for this species at this time. This information provides foundational insights into the seasonal, biological, and anthropogenic drivers of recreational angler reef fish effort along the west coast of Florida. This model, or related frameworks, could be valuable in forecasting future trends in recreational effort along the west coast of Florida specifically and the Gulf of Mexico more generally, and may be instrumental for managers seeking to comprehend the consequences of changes to seasonal reef fishery management.

Commercial catch of Caribbean spiny lobsters (Panulirus argus) in Florida was highly correlated with the abundance of pueruli on artificial collectors. Each lunar month from 1994–2023, we counted postlarvae on artificial collectors at two locations in the Florida Keys (USA). We compared various indices of puerulus settlement and commercial landings. Significant correlations between postlarval indices and the sum of August and September commercial landings were identified at one sampling location. Commercial landings in these first two months of the fishing season likely represent a better index because, as the fishing season progresses, fishing effort and landings are influenced more by non-recruitment factors such as tropical disturbances, catch levels, and the price of lobster. The postlarval index with the highest correlation to landings included the months with peak settlement between January and June in the year prior to the fishing season (p < 0.001). The timing of the postlarval index and range of months indicates that it takes between 14- and 20-months post-settlement for a lobster to enter the fishery and that these peak settlement pulses drive landings in the commercial fishery. The correlation between postlarval settlement and fishery landings suggests that the quantity of postlarvae — and not post-settlement processes — is the primary driver of the spiny lobster population in Florida. Results from this study also indicate that postlarval settlement levels have declined over the past 30 years. As a population that relies heavily on postlarval supply from outside of Florida, this highlights the need for future research into the cause of the decline and any potential link to spawning stock biomass, particularly considering declining landings Caribbean-wide.

Conceptual models are simplified representations of the main components and processes of a dynamic system, the mechanisms by which they are related, and the ways they are observed (i.e., the data generating processes). Constructing a conceptual model (CM) should be the first step when planning a new stock assessment or updating previous assessments, because it can improve the modelling process by guiding the workflow and “modelling what to model”. CMs should be built by summarizing information about a system while also proposing hypotheses or assumptions about the uncertainties and unknown aspects. Several steps are necessary to build a CM: 1) gather known information about the species and the fisheries that interact with it, 2) state the objectives of the stock assessment, 3) define the spatial scale, 4) define the temporal scale, and 5) outline components and processes of the system (biological, fisheries and observation processes) and what drives them. Initial draft CMs should be based on the best available science and constructed using the fundamental principles of ecology, socioecology, fisheries and other relevant sciences. CMs offer a framework for integrating knowledge across domains, and benefit from an elicitation process. The elicitation process is a set of deliberate activities (e.g., workshops) that allow other experts and relevant parties to contribute with their knowledge to enrich draft CMs. CMs are not static entities but rather dynamic constructs that can identify future research directions and evolve to incorporate new insights and knowledge. Fisheries systems for highly migratory pelagic species in the Pacific Ocean (north Pacific Albacore tuna, eastern Pacific Dorado, and south Pacific Swordfish) are used as examples to illustrate how to develop CMs, and demonstrate improvements to the subsequent assessment models following development of the CMs.