Fisheries Research最新文献

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.

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 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.

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.

Globally, marine taxa and their associated ranges are negatively impacted by climate change, including ecologically and socioeconomically important marine mega-decapods. Given their ecological and socioeconomical importance, comprehending the current and future impacts of climate change on marine mega-decapod ranges is of the utmost importance. In this paper, a systematic literature review is conducted on Brachyuran, Anomuran, Astacidean, and Achelatan range responses to climate change. In total, 48 papers were included in this review, with 76 species and 101 range responses reported. We identified trends in study conductance, range responses and associated consequences. Our results show that there is a spatial discrepancy in the distribution of study locations, as well as a taxonomic bias towards studying Brachyuran species. Additionally, our results reveal that the majority of species’ ranges are affected, with range expansions, shifts and contractions being the most commonly recorded. Moreover, a general poleward movement into cooler waters is observed for many species, namely 69 % of all recorded range responses, whilst an offshore movement is witnessed to a lesser extent (18 %). Additionally, a greater number of observed range responses were reported than modelled/predicted range responses. Range shifts will cause a variety of negative ecological impacts, such as exacerbating population declines, increasing competition and spreading disease. Further, range shifts will also create a number of socioeconomic issues, due to commercial and non-commercial species being equally affected by climate change. This is the first and most detailed quantification of marine mega-decapod range responses to climate change and provides key data on range response trends, so that appropriate future conservation strategies can be formulated, and negative socioeconomic impacts can be mitigated.

Despite its significant economic importance and intensive exploitation worldwide, the Atlantic bluefin tuna (ABFT) lacks the essential parameters required to estimate its abundance using acoustic methods at the most used 38 kHz frequency. This paper presents in situ measurements of target strength (TS; dB re 1 m²) for ABFT in dorsal aspect obtained from a baitboat in the Bay of Biscay, using a 38-kHz split-beam echosounder. A linear regression model was fit between TS and fork length (FL; cm) based on data from nine live-bait fishing operations. To mitigate potential bias due to double counting, TS measurements were filtered with fish tracking. The range of modal TS values per set was from −38 to −17 dB for modal tuna body fork lengths between 55 and 150 cm, that is, a rather thorough range of sizes including ABFT juveniles and adults. The linear regression resulted in a TS-length relationship characterised by a slope of 36.9 dB and an intercept of −101.6 dB, with a coefficient of determination R² = 87 %. When the slope of the TS-length relationship was forced to 20, the intercept (b₂₀) was −68.5 dB (R² = 79.5 %). The acoustic parameters presented in this work are key to providing an alternative to the uncertainties associated with the traditionally used fishery-dependent abundance indices of ABFT in the Bay of Biscay and abroad.

Holothuria poli is one of the most in-demand sea cucumber species and has attracted the interest of markets in Mediterranean regions. The present study is the first attempt to determine the reproductive cycle of H. poli in a coastal area of the Central Aegean Sea. Samples of H. poli as well as environmental and biometric data were collected monthly for 1 year. The sample population exhibited a female predominance, a size at first maturation of 156.3 mm and a distinctive reproductive pattern that reached its mature stage in the summer months. These findings contribute to the overall understanding of the reproductive physiology of the species and provide information for the sustainable management of sea cucumber stocks in the Hellenic Seas.