ICES Journal of Marine Science: Journal du Conseil

Bacheler, Nathan M

doi: 10.1093/icesjms/fsad206pmid: N/A

Traps (or pots) are one of the oldest and most widespread scientific survey gears for fish and decapod crustaceans around the world. Here, I review and synthesize the extensive scientific literature describing the various benefits and drawbacks of using traps as a survey gear in scientific studies. The widespread use of traps in fish and decapod surveys is due to several characteristics like their low cost, flexible design, ease of use, ability to fish unattended, and being amenable to pairing with other gears. However, there are a number of significant drawbacks of using traps, including highly variable catches due to environmental fluctuations or behavioral interactions or lost traps that continue catching and killing animals, that must be considered and accounted for when initiating trap surveys. This study highlights the types of habitats and species most and least suited for monitoring by traps, and emphasizes the importance of matching the goals and objectives of a trap survey with the correct trap design, mouth entrance, bait type, soak time, and pairing of gears. Pilot studies are also recommended before surveys are initiated to quantify the selectivity patterns of traps and identify the various factors that may influence trap catch.

Tam, Jamie C; Parlee, Courtenay E; Campbell-Miller, Jill; Bellanger, Manuel; Bentley, Jacob; Pourfaraj, Vahab; Andrews, Evan J; Eger, Sondra L; Cook, Adam M; Beaulieu, Gabrielle

doi: 10.1093/icesjms/fsad172pmid: N/A

Understanding social-ecological systems (SESs) is an important part of ecosystem-based management (EBM). One of the main decision support frameworks to develop scientific advice for EBM is integrated ecosystem assessments (IEAs). Human dimensions in SESs are primarily captured through indicators derived from three social sciences: economics, anthropology, and sociology. The breadth of social sciences and humanities (SSH) research is much greater than those three fields, but they are generally underused in natural science-based decision support processes such as IEAs. Greater contributions of SSHs can enhance IEAs through various direct (e.g. to develop indicators) and indirect ways (e.g. to establish and maintain ethical practices). We examine a wider range of SSH disciplines and conclude that scientific advice processes that inform EBM can benefit from broader integration of SSH theories and methods through themes of contextualizing, facilitating, communicating, evaluating, and anticipating. We see this an opportunity to both widen the vocabulary used to describe social scientists and those who work in humanities in IEAs, and apply the underlying worldviews used to conduct SSH research to fundamentally enhance the IEA process and to further progress in EBM.

Mofokeng, R P; Faltynkova, A; Alfonso, M B; Boujmil, I; Carvalho, I R B; Lunzalu, K; Zanuri, N B Mohd; Nyadjro, E S; Puskic, P S; Lindsay, D J; Willis, K; Adyel, T M; Serra-Gonçalves, C; Zolich, A; Eriksen, T S; Evans, H-C; Gabriel, D; Hajbane, S; Suaria, G; Law, K L; Lobelle, D

Bojesen, Troels Arnfred; Denechaud, Côme; Malde, Ketil

doi: 10.1093/icesjms/fsad170pmid: N/A

Otoliths are a central information source for fish ecology and stock management, conveying important data about age and other life history for individual fish. Traditionally, interpretation of otoliths has required skilled expert readers, but recently deep learning classification and regression models have been trained to extract fish age from images of otoliths from a variety of species. Despite high accuracy in many cases, the adoption of such models in fisheries management has been slow. One reason may be that the underlying mechanisms the model uses to derive its results from the data are opaque, and this lack of legibility makes it challenging to build sufficient trust in the results. Here, we implement a deep learning model that instead of age predicts the location of annotation marks for each of the annuli. This allows an expert to evaluate the model’s performance in detail. The quality of the annotations was judged by a panel of four expert otolith readers in a double-blinded randomized survey. Using a scale from 1 to 5, the generated marks received an average quality score of 4.22, whereas expert annotations received an average score of 4.33. By counting the marks to determine fish age, we obtained an agreement between expert and model annotations of 64% on our test set, which running the model stochastically increased to 69%. Stochastic sampling yields further benefits, including an explicit measure of the model’s uncertainty, the post hoc likelihood of the different age classes for each otolith, and a set of alternative annotation sequences that highlight the structure of the annuli.

Millar, Russell B

doi: 10.1093/icesjms/fsad171pmid: N/A

Methods for jointly estimating both the size-specific relative retention and absolute retention (retention probability) of two experimental trawl gears are considered. One approach would be to undertake comparative fishing of both gears, from which their comparative catchability can be estimated directly. If comparative catchability can be corrected for differing sampling effort and fishing efficiency of the two gears, then relative retention can be estimated. Furthermore, if a suitable functional form of the absolute retention curve is assumed, then estimates of absolute retention can potentially be obtained. However, these estimated retention curves are seen to have extremely large statistical variability and will not be useful in practice. On the other hand, if the gears are each fished with a non-selective control, then absolute retention can be directly estimated, from which estimates of relative retention can immediately be obtained. However, these estimates of relative retention have greater variability than would be obtained by comparative fishing with the same level of sampling effort. It is shown that a hybrid selectivity design that includes both comparative fishing of the experimental trawls and fishing with a non-selective control provides a more balanced approach. An extensive simulation study is conducted using scenarios based on recently published work on selectivity experiments targeting cod (Gadus Morhua) and hoki/blue grenadier (Macruronus novaezelandiae).

Banda, Shamiso; Pistorius, Pierre; Collet, Julien; Corbeau, Alexandre; Weimerskirch, Henri; Pajot, Adrien; Keys, Danielle Z; Orgeret, Florian

doi: 10.1093/icesjms/fsad176pmid: N/A

Bycatch risk assessments typically rely on spatial overlaps between seabirds and fishing vessels but should also consider seabirds’ position in the attraction spectrum. Investigating seabird-fishery interactions in relation to habitat use is vital for species-specific risk assessments. To address this, we studied interactions between sooty albatrosses (SA) and white-chinned petrels (WCP) with fisheries. GPS data from 20 SA and 18 WCP individuals from Marion Island were analysed alongside Automatic Identification System-derived boat locations over two breeding seasons. We calculated encounter and attraction rates and correlated them with marine habitat characteristics. SA interactions occurred in deeper, warmer waters compared to their foraging habitat when vessels were absent, with 20% of individuals encountering and only 5% being attracted to boats. In contrast, WCP interactions occurred in shallow, warm South African shelf waters, consistent with their typical foraging habitats, with 72% encountering and 56% attracted to boats. These results highlight the need for continued reinforcement of mitigation measures for WCP. Despite the low attraction rates for SA, ongoing vigilance is required due to their smaller population size, which heightens the potential impact of illegal fisheries. The comparison of species along an attraction spectrum contributes to refining risk assessments and informs species-specific conservation strategies.

Hiddink, Jan Geert; Coleman, Matthew T; Brouwer, Stephen; Bloor, Isobel S M; Jenkins, Stuart R

doi: 10.1093/icesjms/fsad178pmid: N/A

Trap fisheries targeting invertebrates are economically important but many of the target species lack stock assessments. One reason for this is the difficulty of estimating density. One important means by which density can be estimated uses the catch rates of baited traps that are spaced at different distances. With declining spacing, the sphere of attraction will increasingly overlap, leading to reductions in catches, allowing for the estimation of the density that is catchable by traps on the seabed. Here we review the analytical methods adopted across a range of studies and find that no consensus on robust methods exists. We propose an analytical method that assumes the trapping area is circular and that the chance of catching an individual declines linearly with distance from the trap. We apply this method to estimate the density and the trapping radius of crabs and gastropods from real and simulated datasets. The method estimated a trapping radius of between 4 and 86 m, and densities that are up to 2.5 times less and 13 times greater than estimates provided in the original sources, illustrating the sensitivity to methodology. In conclusion, we provide and test a standardized method to estimate the density of benthic invertebrates.

Pascoe, S; Curtotti, R; Hoshino, E; McWhinnie, S; Schrobback, P

doi: 10.1093/icesjms/fsad180pmid: N/A

In many low-valued fisheries, the quantity and types of data that might be available to support fisheries management are often limited. Generally, information on the economic performance of the fishery is low in priority in these fisheries. Basic catch and effort information, however, may contain implicit information about economic performance of the vessels. From these data, technical efficiency scores and measures of capacity utilization can be derived. The technical efficiency score can provide a proxy measure of the distribution of economic performance, while changes in capacity utilization theoretically reflect changes in the economic conditions in the fishery. Given this, changes in these measures over time should also reflect changes in economic outcomes and performance. To test this, we use data from a data-rich fishery, including catch and effort information as well as detailed economic information (i.e. vessel-level profitability). Key technical performance measures are estimated using data envelopment analysis and compared with the economic performance measures. We show that these technical performance measures can provide useful indicators of changes in economic performance when economic information is not available.

Hiddink, Jan Geert; Charles, Ryan; Moore, Alec B M

doi: 10.1093/icesjms/fsad183pmid: N/A

Detecting changes in the distribution and abundance of marine species that are cryptic or occurring in very low abundances is difficult, but essential for assessing their status and informing management. One way of quantifying these changes is through the collation of opportunistic records. We reconstruct the population trajectory and distribution of the common stingray Dasyatis pastinaca around Great Britain, using opportunistic records, mostly obtained by recreational anglers. We tested if D. pastinaca declined in abundance and body size in response to fishing and if their distribution has shifted northwards in response to warming seas. We obtained 518 records covering the period 1838–2020. After correcting for observation effort, D. pastinaca catches reported by anglers showed no long-term trend over 50 years, but decreased from 1970 to 1995 and an increase in abundance since 1995. While records of species occurrence were found around much of Great Britain, nearly all were from south of 54° latitude, and records have contracted southwards since 2000. No trend in maximum size through time was detected. In conclusion, we did not find support for the hypothesized declines in abundance and body size or a northward shift in distribution of D. pastinaca and instead found a southward contraction.

Strand, Nina; Glover, Kevin A; Meier, Sonnich; Ayllon, Fernando; Wennevik, Vidar; Madhun, Abdullah; Skaala, Øystein; Hamre, Kristin; Fjelldal, Per Gunnar; Hansen, Tom; Niemelä, Eero; Knutar, Sofie; Fjeldheim, Per Tommy; Solberg, Monica F

doi: 10.1093/icesjms/fsad184pmid: N/A

Each year thousands of farmed Atlantic salmon escape from seawater net pens, and introgression has been documented in a range of wild populations. Due to greater experience in the wild, escapees that have been on the run for a longer period, and successfully transitioned to a wild diet (classified: “early escapees”), could potentially have a higher spawning success and contribute more to introgression than those that have been on the run for a shorter period and/or have not transitioned to a wild diet (classified: “recent escapees”). This is the first study to examine how the escape history of farmed Atlantic salmon captured in multiple rivers and coastal fisheries, varies in time and space. During 2011–2021, adult farmed escaped salmon were captured in four rivers and at six coastal sites in Norway. The level of linoleic acid, a terrestrial fatty acid high in commercial salmon feeds but low in the natural diet of wild salmon, was used to classify the farmed salmon as early or recent escapees. We observed temporal declines in the relative proportions of escaped vs. wild salmon in the catches, and the relative proportion of early vs. recent escapees in the most southern river (driven by samples from 2011 to 2015). Overall, 14% of the escaped salmon caught in the period were classified as early escapees. The relative proportion of early escapees was lower in the two southernmost rivers (21.2% and 6.30%), as compared to the coastal fisheries (40.9%) and the northernmost river (77.6%). Both aquaculture–management regulations and production strategies have likely influenced these observations.