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Used vs. new: Does it have consequences for the performance of fishing gear?
Get PDFSea trials to test size selectivity equipment in trawls are often limited in time because they are costly, and the results can be influenced by multiple factors that are often overlooked. In the Barents Sea gadoid trawl fishery, the use of a size sorting grid in front of the codend is compulsory. The flexigrid, a netting section containing two flexible grids, is the most widely used grid section in this fishery. However, earlier selectivity studies with this device have shown inconclusive results. It has been speculated that the differences observed resulted from the difference in age and usage of the grid sections in the studies compared. To reveal whether potential changes in the device construction over time can lead to differences in size selection properties, we performed comparative fishing trials where we compared a brand new flexigrid section and a well-used flexigrid section used continuously by a commercial trawler for approximately four years. The results showed that the new flexigrid released significantly more cod below ∼60 cm than the used flexigrid. However, when the grids were fished with a subsequent diamond mesh codend, there was no difference in the overall selectivity of the two gears, meaning that the size selectivity in the codend compensates for the potential reduction in selectivity performance of the grids. This study shows the importance of considering the age and earlier use of size selection devices like sorting grids before they are compared with other devices, as their size selection properties can change significantly over time and with use.publishedVersio
Antarctic krill and ecosystem monitoring survey off the South Orkney Islands in 2023
Get PDFEnvironmental monitoring along 5 set transect lines off South Orkney Islands in the Southern Ocean have been carried out annually (since 2011) by the Institute of Marine Research, Norway. Data are used to calculate biomass of Antarctic krill (Euphausia superba) as well as mapping distribution and demographic composition of krill, but also other macrozooplankton and fish taxa. Visual sightings of cetaceans and pinnipeds are registered systematically along the transects during daylight hours. During this year's survey, a pilot photo-drone project was also undertaken to investigate the potential of employing this type of technology to monitor body-size of individual whales to form the basis for calculating energetics and prey needs. Personnel were also deployed on Powell Island with breeding chinstrap penguins to satellite-tag penguins. At the same time, we maneuvered an unmanned sail drone, fitted with an echosounder, via satellite communication into what is known to be the preferred feeding area for chinstraps that breed at Powell Island. This data will be used to study swarm types in relation to penguins foraging strategies as well as assessing potential spatiotemporal overlaps with fisheries. Herein we report on the survey activities from 2023 and present some preliminary results.Antarctic krill and ecosystem monitoring survey off the South Orkney Islands in 2023publishedVersio
Interaction of temperature and feed ration on male postsmolt maturation of Atlantic salmon (Salmo salar L.)
Get PDFEarly maturation of Atlantic salmon male postsmolts is undesirable in aquaculture due to its negative impact on growth, welfare and seawater adaptation, however it is an increasing problem under intensive rearing conditions. The effect of temperature and feeding ration on sexual maturation during the induction of smoltification was tested with a 3 × 2 factorial design including three temperatures (8, 12.5 and 18 °C) and two feeding rations (100% and 67%), from 28 October 2018 to 30 May 2019. Fish in the six resulting treatments (1800 parr, initial mean weight 23.1 ± 7.2 g) were reared in flow-through under continuous light (LD24:0) except for a 5-week winter signal (LD12:12) introduced on 4 February 2019 to induce smoltification. A major effect of temperature determining the life history pattern of each group was observed. At 18 °C, a majority of the males were maturing in May under both rations (100% males in 18–100% and 88.9% males in 18–67%). Fish at 18 °C experienced an early activation of the BPG (Brain-Pituitary-Gonad) axis and displayed very poor signs of smoltification. At 12.5 °C, early maturation was also present, although at lower proportion than at 18 °C and more dependent upon feed ration (40% of males maturing in 12.5–100%, 8.6% in 12.5–67%). Salmon at 12.5 °C displayed the best growth within each feed regime, some early signs of smolting but subsequent low Na+, K+- ATPase activity after the winter signal. At 8 °C, salmon showed best signs of smoltification and lowest growth, while no males matured. The feed restriction had a minor effect on maturation at 18 °C but a greater impact at 12.5 °C, evidenced by significant differences between 12.5–100% and 12.5–67% in gonadosomatic index, plasma 11-ketotestosterone, insulin-like growth factor-I, and pituitary fshb (follicle stimulating hormone β-subunit gene) transcription. Onset of maturation was associated with the photoperiod change from short to long daylength, which probably also induced a slight activation of the BPG axis in non-maturing groups. Our results suggest that postsmolt producers must be cautious when using sustained high water temperatures, or the risk of early maturation and poor hypo-osmoregulatory performance will increase significantly. In addition, reducing the feeding ration will not help decrease incidence of maturation without significantly affecting growth.publishedVersio
Life history traits for Ophryotrocha craigsmithi (Wiklund, Glover & Dahlgren, 2009), a candidate species in integrated multitrophic aquaculture
Get PDFOphryotrocha craigsmithi (Wiklund, Glover & Dahlgren, 2009) has repeatedly been observed in high densities at salmonid fish farms in Norway and has been shown to feed on the organic waste released during fish production. This species has therefore been pointed out as a candidate for the benthic component of integrated multitrophic aquaculture (IMTA). Little is known about the life history traits of Ophryotrocha species found at greater depths in temperate waters. Insight into life traits is of key importance in evaluating the bio-mitigation and harvest potential of (benthic) species within IMTA systems. In this study, we aimed to describe key life history traits for O. craigsmithi, such as growth, reproductive pattern, and offset of reproduction. The main findings are as follows: (I) O. craigsmithi exhibits early sexual maturation and rapid growth, going from 5 to 16 mm in length in 8 weeks; (II) their estimated lifetime is approximately 15 weeks with a generation time of 4 weeks; (III) there are strong indications that they are gonochoric semicontinuous spawners; (IV) the majority of mature eggs ranged from 120 to 150 µm; and (V) the larvae developed into a free-swimming stage after approximately 1 week. To this end, we present a framework for assessing the suitability of deposit-feeding polychaetes as candidate species in IMTA, considering environmental adaptiveness, production potential, as well as carbon and nitrogen mitigation capacity. On the basis of this, O. craigsmithi shows a high suitability as an extractive farmed species in benthic IMTA.publishedVersio
Migratory behavior of aggregating male Tiger Grouper (Mycteroperca tigris) in Little Cayman, Cayman Islands
Get PDFTiger Grouper (Mycteroperca tigris) form fish spawning aggregations (FSAs) around the winter full moons (typically January through April) in the Caribbean. Males defend territories to attract mates in a lek-like reproductive strategy. Prior studies have documented rapid declines in populations with FSA-associated fisheries. This study examines the migratory behavior of adult male Tiger Grouper in Little Cayman, Cayman Islands, to better understand the impacts of aggregation fishing. As part of the Grouper Moon Project, we acoustically tagged ten spawning male Tiger Grouper at the western end of Little Cayman in February 2015. Using a hydrophone array surrounding the island, we tracked the movements of the tagged fish for 13 months. We observed 3 migratory strategies: resident fish (n = 2) that live at the FSA site, neighboring fish (n = 5) that live within 4 km of the site, and commuter fish (n = 3) that travel over 4 km for spawning. Fish began aggregating 2 days before the full moon and left 10–12 days after the full moon, from January to May. Regardless of migratory strategy, all tagged fish that aggregated after February 2015 returned to the west end FSA. However, in January 2016, one fish appeared to attend a different FSA closer to its presumed home territory. Tiger Grouper may establish multiple FSAs around Little Cayman, and males appear to attend FSAs near their home territories. Protracted spawning seasons, FSA site infidelity, and putative FSA catchments should all be considered to ensure sustainable fisheries management for this important species.publishedVersio
Host genotype and microbiome associations in co-occurring clonal and non-clonal kelp, Ecklonia radiata
Get PDFA fundamental question in holobiont biology is the extent to which microbiomes are determined by host characteristics regulated by their genotype. Studies on the interactions of host genotype and microbiomes are emerging but disentangling the role that host genotype has in shaping microbiomes remains challenging in natural settings. Host genotypes tend to be segregated in space and affected by different environments. Here we overcome this challenge by studying an unusual situation where host asexual (5 clonal lineages) and sexual genotypes (15 non-clonal lineages) of the same species co-occur under the same environment. This allowed us to partition the influence of morphological traits and genotype in shaping host-associated bacterial communities. Lamina-associated bacteria of co-occurring kelp sexual non-clonal (Ecklonia radiata) and asexual clonal (E. brevipes) morphs were compared to test whether host genotype influences microbiomes beyond morphology. Similarity of bacterial composition and predicted functions were evaluated among individuals within a single clonal genotype or among non-clonal genotypes of each morph. Higher similarity in bacterial composition and inferred functions were found among identical clones of E. brevipes compared to other clonal genotypes or unique non-clonal E. radiata genotypes. Additionally, bacterial diversity and composition differed significantly between the two morphs and were related with one morphological trait in E. brevipes (haptera). Thus, factors regulated by the host genotype (e.g. secondary metabolite production) likely drive differences in microbial communities between morphs. The strong association of genotype and microbiome found here highlights the importance of genetic relatedness of hosts in determining variability in their bacterial symbionts.publishedVersio
Pilot project for the short-time live storage of bluefin tuna — Trials onboard MS Vestbris 2023
Get PDFNorway was historically a major bluefin tuna (BFT) harvesting country. However, fishing for this species has experienced low profitability. One potential solution is short-term live-storage so that the market can be supplied on demand. Further, storing BFT allows a more controlled slaughtering of the fish, resulting in better quality and fish welfare. A pilot project was established in 2020 to address knowledge gaps related to BFT live-storage in Norway. This document summarizes the findings from sea trials in 2023.Pilot project for the short-time live storage of bluefin tuna — Trials onboard MS Vestbris 2023publishedVersio
Addressing class imbalance in deep learning for acoustic target classification
Get PDFAcoustic surveys provide important data for fisheries management. During the surveys, ship-mounted echo sounders send acoustic signals into the water and measure the strength of the reflection, so-called backscatter. Acoustic target classification (ATC) aims to identify backscatter signals by categorizing them into specific groups, e.g. sandeel, mackerel, and background (as bottom and plankton). Convolutional neural networks typically perform well for ATC but fail in cases where the background class is similar to the foreground class. In this study, we discuss how to address the challenge of class imbalance in the sampling of training and validation data for deep convolutional neural networks. The proposed strategy seeks to equally sample areas containing all different classes while prioritizing background data that have similar characteristics to the foreground class. We investigate the performance of the proposed sampling methodology for ATC using a previously published deep convolutional neural network architecture on sandeel data. Our results demonstrate that utilizing this approach enables accurate target classification even when dealing with imbalanced data. This is particularly relevant for pixel-wise semantic segmentation tasks conducted on extensive datasets. The proposed methodology utilizes state-of-the-art deep learning techniques and ensures a systematic approach to data balancing, avoiding ad hoc methods.Addressing class imbalance in deep learning for acoustic target classificationpublishedVersio
Annotating otoliths with a deep generative model
Get PDFOtoliths 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.publishedVersio
Co-designing marine science for the ocean we want
Get PDFThe United Nations Decade of Ocean Science for Sustainable Development requires that all of the Actions it endorses have concrete plans to involve stakeholders in the co-creation of ocean science. As a result, we have a unique opportunity to test different approaches to stakeholder engagement to see what works and what does not. Here, we feature short essays in the “Food for Thought” series in which leaders from Decade-endorsed Actions describe how they plan to incorporate stakeholders in the co-design, co-production, and co-delivery of ocean science and how they will measure whether these approaches were successful. We also invited submissions to the journal’s “Stories from the Front Lines” series, in which authors were asked to share unvarnished accounts of the lessons learned from previous efforts to co-design ocean science. We hope that these initial articles will be the beginning of an ongoing series in which new Decade Actions will also document their plans to implement, monitor, and measure the success or failure of these approaches.publishedVersio