Fisheries Research最新文献

In New South Wales (NSW), Australia, the majority of the commercial catch of eastern rock lobster (Sagmariasus verreauxi) is captured from traps fished on the mid and outer continental shelf in depths 50 – 220 m (119.5 t in 2021–22: 66.5 % of landings). Hermit crabs are the greatest bycatch from this fishery. The Fishery Management Strategy (2007) for the NSW lobster fishery, recognised the need to quantify by-catch species associated with lobster catches with an emphasis on increasing knowledge of the populations of hermit crabs along the NSW coast. An observer-based survey during 2008 and 2009 quantified by-catch from the fishery including, for each hermit crab species identified: (i) spatial and temporal distribution; (ii) relative abundance (number per trap-lift), and (iii) size distribution (shield length, SL). A total of 5782 hermit crabs were collected from 70 offshore trips comprising 722 trap-lifts. No hermit crabs were collected from 73 inshore trips (< 50 m depth) comprising 3232 trap-lifts, due to the low number (seven) of hermit crabs observed. Five species of hermit crab were identified. Three species were captured in very low numbers: Dardanus crassimanus (n=2), Dardanus pedunculatus (n=2) and Dardanus australis (n=1). The striated hermit crab (Dardanus arrosor; Herbst, 1796; n = 1970) and the stridulating hermit crab (Strigopagurus strigimanus; White, 1847; n =3812) were common in all latitudinal zones (30° - 37°S) and offshore depths (50–220 m) sampled. Abundance of D. arrosor decreased southward in contrast to S. strigimanus that showed the opposite pattern. Both species were more abundant on the outer-shelf than the mid-shelf. Mean SL of males was greater than females for both species across all latitudes on both the mid- and outer-shelf. Annual catches by the commercial fishery, by latitude and depth, were estimated for each species. This research provides a baseline for monitoring and interpretation of any future changes in the distribution and abundance of hermit crab species along the NSW coast.

The installation and operation of floating offshore wind power is an integral component of societal transition to renewable energy generation where fixed bottom offshore wind is not possible. However, it will cause unique ecosystem changes. To disentangle the effects of offshore wind installations from the concurrent effects of climate change and the fishing practices on commercially significant resources, we must develop detailed characterizations of the resources before development occurs. In the Gulf of Maine, American lobster is the most commercially and culturally important fishery. At the time of writing, this is the largest fishery by value in North America. Our understanding of baseline localized parameters (such as catch per trap at the spatial scale of individual turbines) should be informed by relationships to environmental, biological, and survey-specific functional drivers of catch. A more mechanistic understanding of catch will allow for strategic adjustments to Post-Deployment fishery responses and ultimately, the development of research- and commercial-scale floating offshore wind development. Here, we used survey data from the New England Aqua Ventus Pre-Construction Commercial Trapping Survey to develop Generalized Additive Models describing seasonal catch per trap for legal and sublegal lobsters. We found fall catch to be nearly twice that of spring. Bottom temperature dynamics could be used to predict catch, and the Fall survey was associated with a warmer temperature regime. By using analytical tools that incorporate environmental heterogeneity, we developed monitoring methods from pre-construction baseline data that will be applicable over the post-construction operating period of an offshore wind farm.

The use of morphology to investigate the population structure of fishes is an increasingly used technique in fisheries science. Understanding population structure helps ensure fisheries sustainability and preserves intraspecific biodiversity, which is key to ecosystem functioning. Here, the landmark-based geometric morphometric technique was utilised for the first time on New Zealand snapper (Chrysophrys auratus), a sought-after fish in both recreational and commercial fisheries. Evidence of regional population structure was found, the most pronounced morphological differences being in the head curvature, body depth, eye size, and caudal peduncle width. There were statistically significant differences in body morphology between all but one of the hypothesised populations, with C. auratus individuals correctly allocated to the appropriate populations 86 % of the time. To test optimal population configuration for management areas, several scenarios were run where individual fish were reassigned to different groups, but there was no improvement in allocation success. However, a scenario that excluded fish near the boundaries of current management areas improved allocation success to 99 %. The morphological findings in this study align with other productivity measures for these populations, suggesting that current stocks are comprised of multiple populations. This population structure must be considered at a management level to prevent localised depletions and conserve crucial intraspecific biodiversity.

Machine learning methods such as random forest regression models are useful tools in ecology when applied correctly, although features inherent to ecological data sets can lead to over-fitting or uncertain predictions. Here, a set of methods are outlined to account for temporal autocorrelation, and sparse, short, or missing data for random forest predictions. Methods are also provided for estimating prediction uncertainty due to the combination of inherent randomness in the random forest algorithm and sparse input data. This suite of methods was used to generate pre-season predictions of total catches with uncertainty for California market squid (Doryteuthis opalescens), the most valuable fishery in California (by ex-vessel value). The methodology presented in this analysis is not only robust, incorporating key cross-validation and hyperparameter tuning techniques from across disciplines, but is also flexible, making it applicable to various ecological and fisheries datasets beyond market squid.

The South Australian Rock Lobster Fishery uses baited pots, traditionally ‘beehive’ in shape, to capture Southern Rock Lobster (Jasus edwardsii). Fishery harvest is controlled through annual quota that is set relative to performance indicators of relative abundance (Catch Per Unit Effort) for legal-size and pre-recruit lobsters. Under quota-based controls, improvements in catch efficiency through alternative pot designs offer an opportunity to reduce input costs and improve net economic return with low risk to stock sustainability. However, for performance indicators such as CPUE to remain robust, any changes in fishing efficiency must be accounted for in stock assessment. This study collected data from 13 fishers over 768 sampling days resulting in five treatments and 14,006 individual potlifts from the South Australian Northern Zone Rock Lobster Fishery. Geo-statistical methods, developed to control for temporal and spatial covariates, and variable lobster abundance, indicated higher catch efficiency of legal-size and undersize lobsters in ‘batten’ pots compared to ‘beehive’ pots. Ratios of mean legal-size catch weight $\left({\hat{\rho }}_{C_W\mathrm{PUE}}\right)$and undersize lobster (number) (${\hat{\rho }}_{\mathrm{PRI}})$from beehive pots to batten pots were estimated to be $0.62$ and $0.68$, respectively. Applying the ratio $\left({\hat{\rho }}_{C_W\mathrm{PUE}}\right)$with respect to effort, fishers adopting batten pot designs may reduce future effort (potlifts) to take quota by up to 38 %. Potential increases in undersize catches of up to 32 % for fishers using batten pot designs would be offset by an overall reduction in effort. The taxonomic composition of bycatch was similar in batten pots and beehive pots. Generally lower catches of all bycatch were observed from batten pots and further reductions in bycatch discard rates would be likely where effort is reduced via their use to take quota. The number of depredated lobsters recorded during testing was similar between batten pots and beehive pots also indicating that reduced effort to attain quota with batten pots could lower the absolute number of dead lobsters landed each season. Methods to account for differences in pot-specific catch efficiency in future harvest strategy decision rules are discussed.

Sustainable fisheries management often requires the modelling of stocks under unfished conditions, when the influence of population densities on animal growth and mortality can be substantial. This can be especially true for species such as spiny rock lobster, which are very habitat specific. Using western rock lobster (Panulirus cygnus) tag-recapture data from adjacent and similar fished and unfished areas, the key life history parameters of natural mortality and growth were examined and compared under different population density scenarios. In an area representative of virgin biomass levels, lobsters exhibited reduced growth rates and a substantially higher rate of natural mortality than in the adjacent, less densely populated fishing grounds. This research highlights the non-stationary nature of growth and natural mortality in this species, a concept which is poorly understood and rarely acknowledged in stock assessment models. Additionally, these results indicate that the perceived benefits of fishery closures, such as spill over and increased reproductive output, may not be as simple as is often assumed, due to the reduced growth and increased mortality of the protected stock relative to the fished population.

The precautionary approach to fisheries management requires accounting of uncertainty to ensure stock sustainability. Most fisheries management is based on a single-species approach, with stocks assumed independent of one another, even though it is known that stocks interact through predation and competition for resources. The strength of these interactions depends on the relative abundance and size/age composition of stocks, but they are usually treated as fixed. Therefore, a key question is: can we simultaneously adopt the precautionary approach for multiple stocks while accounting for these interactions? Here we examine the impact of stock interactions on calculations of precautionary reference points for nine stocks in the North Sea. We combined four multispecies models using an ensemble model to rigorously quantify uncertainty and explore the rates of fishing mortality that leads to groups of stocks being fished according to the precautionary approach. We found that relaxing the assumption of stock independence meant that no fishing at all was only precautionary for six of nine stocks, and no fishing strategy was precautionary for all nine. We suggest that it is necessary to account for multispecies interactions when calculating precautionary reference points.

Fisheries regulations require detailed catch reporting on commercial fishing vessels. Vital components for the sustainable management of fish stocks include a robust estimate of the number of fish caught and the species composition. Catch recording is often done manually by human observers on fishing vessels. Human observers are costly, and consistent data streams can be subject to observer availability and the weather. On-vessel cameras (electronic monitoring, EM) are a growing alternative to human observers. However, on-land human auditors are required to review hundreds of hours of videos recorded during fishing trips that can last for weeks. In this paper, a framework is presented to automatically detect fish in EM videos, count the total fishing events, and classify the fish species. For this purpose, a deep learning and computer vision-based model is developed to efficiently detect fish and fishers onboard a vessel. Secondly, a vision-based tracking pipeline tracks the detected fish and counts the total fishing events in the videos. Thirdly, the extracted fishing events are classified through a deep learning-based fish species classifier, to provide the distribution of different fish species caught for a fishing trip. For our experiments, the datasets were prepared using the electronic monitoring data of multiple fishing trips of a fishing vessel. The videos were recorded on Australian longline vessels targeting tunas and billfish. For the fish detection task, video frames were extracted and labelled manually to provide a digital ground-truth. For the fish species classification task, hundreds of fish images of multiple species were cropped to provide a training dataset for the fish classifier. For the fish counting task, manual counts for the fishing events of individual fish species were generated for the test fishing trips. The developed fish and fisher detector achieves a mean Average Precision of 87.0 % for fish and 94.0 % for fishers on test video frames. The fishing event detection pipeline achieves an Average Precision of 81.0 % and an Average Recall of 74.5 % on test videos. The fish species classifier achieves an Accuracy (Top-1) of 91.11 % for the classification of cropped fish images and 89.05 % for the classification of extracted fishing events from the videos. Experimental results show that our proposed computer vision and artificial intelligence-based solution for video analysis has great potential to automate the auditing process from electronic monitoring footage and contribute to the sustainable management of fish stocks.

Spiny (rock) lobsters occur globally and, although harvest is dominated by commercial fisheries, it is important to account for recreational harvest in stock assessments and fisheries management. This paper provides a contemporary review of recreational fishing for five spiny lobster species in Australia and New Zealand. Each jurisdiction has established approaches for collecting data which best meet their information needs (telephone-diary or telephone-recall surveys, charter logbooks, tag reporting). Jurisdictions with specific spiny lobster licences (Western Australia, Tasmania) or mandatory reporting (charter logbooks in Western Australia, tag reporting in Victoria) use these registers as a sampling frame for annual reporting of participation, fishing effort, catch (numbers) and harvest (tonnes). All other jurisdictions use a general fishing licence or general population sampling frame for telephone-diary surveys to provide periodic reporting of catch and harvest. Annual participation in spiny lobster recreational fishing was highest in Western Australia (35,236 ± SE 626 fishers in 2022–23), followed by Tasmania (13,715 ± SE 1067 fishers in 2022–23) and Victoria (5516 fishers in 2020–21). Annual recreational harvest of all spiny lobster species, combined for the most recent data collection period in each jurisdiction, was 830 tonnes; consisting mostly of Western Rock Lobster (Panulirus cygnus) from Western Australia and Southern Rock Lobster (Jasus edwardsii) from Tasmania and New Zealand. This review illustrates the various spatial scales of monitoring, reporting and assessment in each jurisdiction. All monitoring provides information on catch and harvest, with some also reporting participation, effort, carapace length and non-catch related variables. The designs underlying these approaches vary from probability-based (opt-out) and census (mandatory), and it is important to understand the benefits and inherent biases of each. Understanding the parallels between jurisdictions offers valuable insights into how to cost-effectively monitor spiny lobster recreational fisheries and integrate this data into stock assessment and harvest strategies to support sustainable fisheries into the future.

Current fishery management practices in both the U.S. Gulf of Maine and southern Norwegian clawed lobster fisheries primarily focus on conserving mature females to maximize egg production. While abundance of adult American lobsters (Homarus americanus) in the Gulf of Maine remains high, declines appear to be on the horizon. Similarly, the European lobster (Homarus gammarus), is facing its lowest recorded population size in southern Norway. Understanding how management strategies and fishing practices impact lobster size structure and spawning potential could inform management to improve resiliency to climate-induced changes. In the Gulf of Maine fishery, egg-bearing (ovigerous) female lobsters are not only protected from harvest, but also v-notched which offers additional protection up to several years. Southern Norway, however, protects egg-bearing females without v-notching. Comparing these fisheries allows us to test the effect of the different management practices and how they interact with key vital rates, including growth and natural mortality rates. We used deterministic size- and age-structured models and empirically estimated growth and molt functions to simulate relative changes in abundance, size structure, egg production, and sex ratios in response to these two female protection strategies. Our findings suggest that in all scenarios, controlling total fishing effort to low or moderate levels - relative to the F > 1 that has been estimated for American lobster - is most important for the effectiveness of size-based restrictions on harvest of larger individuals. Both forms of female protection enhance overall egg production in both species across levels of fishing intensity, but also result in a skewed sex ratio in favor of females and a more pronounced size disparity between female and male lobsters. Moreover, our results suggest that American and European lobster populations exhibit differential responses to the management strategies, likely due to variations in estimates of natural mortality rates and growth rates. Our results highlight the sensitivity of management effectiveness to assumptions regarding the underlying biology, but also provide a clear message that current intense fishing practices have likely depleted the ability of both species to compensate for fishing mortality in the long term.