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This important and informative new book outlines and discusses details of the basic principles and methods that are central to any study of fish condition, from a fish ecology and fisheries biology perspective. Condition and Health Indicators of Exploited Marine Fishes describes the potential capacities of condition indicators, providing examples showing the use of these indicators to solve practical problems in connection with fish ecology and fisheries research. By focusing on wild fish populations, the book complements the increasing number of scientific works that are contributing to show how fish condition studies are key to reveal problems in marine aquaculture, the effects of pollution, fish disease, and the importance of fish in human nutrition and medicine. Condition and Health Indicators of Exploited Marine Fishes provides a comprehensive introduction to the study of fish condition that will assist advanced undergraduate and postgraduate students, researchers and professionals, working in marine ecology and biology, fisheries biology, environmental sciences and fish pathology. All universities and research establishments where biological and environmental sciences, fisheries and aquaculture are studied and taught should have copies of this book on their shelves.

\"This book is the most extensive coverage of Canadian Marine fishes ever to be published. 200 species in 52 families found in Canadian Arctic waters. A wide-ranging general introduction looks at the history of research, fish habitats, climate fisheries, scientific names, fish structure and the collection and preservation of fishes. Finally range maps showing distributon across Arctic Canada are included for all species.\"--Provided by publisher.

Plastic contamination is ubiquitous, with plastic found in hundreds of species of aquatic wildlife, including fish. Lacking a broad and comprehensive view of this global issue across aquatic environments, we collated and synthesised the literature that focuses on microplastic ingestion in fish from marine, freshwater and estuarine environments. First, we assessed how the approaches used to investigate microplastic in fish have changed through time, comparing studies globally. A greater understanding of this changing landscape is essential for rigorous and coherent comparisons with only 42% of published studies following recommended approaches of chemical digestions and verifying plastic via polymer identification. Then, using this subset of studies, we found that 49% of all fish sampled globally for microplastic ingestion had plastic (average of 3.5 pieces per fish), with fish from North America ingesting more plastic than fish from other regions. We then evaluated the role of environment, habitat, feeding strategy and source (i.e. aquaculture or wild-caught) in the ingestion of microplastic. Research from marine environments dominated (82% of species) but freshwater fish ingested more plastic, as did detritivores, fish in deeper waters and those from aquaculture sources. By collating global microplastic research we identified regional disparities and key knowledge gaps that support research towards freshwater environments and aquaculture sources. Overall, we highlight the need for consistent guidelines in methods used to evaluate microplastic in fish, to ensure data are unambiguous, comparable and can be widely used to support mitigation and management strategies, inform potential policy actions, and evaluations of environmental, food safety, and human health goals.Graphic abstract

Sent out for a swim in the deep sea, Tiddler, a young fish who just can't keep still, sees many interesting creatures and one very dark cave.

The climate regime in the eastern Bering Sea has recently been dominated by a pattern of multi-year stanzas, in which several successive years of minimal sea-ice formation and warm summer temperatures (e.g., 2002–2005, 2014–2017) alternate with several years of relatively extensive sea-ice formation and cold summer temperatures (e.g., 2006–2013). This emerging climate pattern may be forcing long-term changes in the spatial distributions of the Bering Sea’s marine fauna. The National Marine Fisheries Service’s Alaska Fisheries Science Center recently conducted two bottom trawl surveys covering the entire Bering Sea shelf from the Alaska Peninsula to the Bering Strait. The first, in the summer of 2010, was conducted during a cold year when the majority of the continental shelf was covered by a pool of cold (< 2 °C) water. The second, in the summer of 2017, was during a warmer year with water temperatures above the long-term survey mean. These two surveys recorded significantly different spatial distributions for populations of several commercially important fish species, including walleye pollock (Gadus chalcogrammus), Pacific cod (Gadus macrocephalus), and several flatfish species, as well as jellyfishes. Population shifts included latitudinal displacement as well as variable recruitment success. The large-scale distributional shifts reported here for high-biomass species raise questions about long-term ecosystem impacts, and highlight the need for continued monitoring. They also raise questions about our management strategies for these and other species in Alaska’s large marine ecosystems.

Monitoring communities of fish is important for the management and sustainability of fisheries and marine ecosystems. Baited remote underwater video systems (BRUVs) are among the most effective nondestructive techniques for sampling bony fishes and elasmobranchs (sharks, rays, and skates). However, BRUVs sample visually conspicuous biota; hence, some taxa are undersampled or not recorded at all. We compared the diversity of fishes characterized using BRUVs with diversity detected via environmental DNA (eDNA) metabarcoding. We sampled seawater and captured BRUVs imagery at 48 locales that included reef and seagrass beds inside and outside a marine reserve (Jurien Bay in Western Australia). Eighty-two fish genera from 13 orders were detected, and the community of fishes described using eDNA and BRUVs combined yielded >30% more generic richness than when either method was used alone. Rather than detecting a homogenous genetic signature, the eDNA assemblages mirrored the BRUVs’ spatial explicitness; differentiation of taxa between seagrass and reef was clear despite the relatively small geographical scale of the study site (~35 km²). Taxa that were not sampled by one approach, due to limitations and biases intrinsic to the method, were often detected with the other. Therefore, using BRUVs and eDNA in concert provides a more holistic view of vertebrate marine communities across habitats. Both methods are noninvasive, which enhances their potential for widespread implementation in the surveillance of marine ecosystems. El monitoreo de comunidades de peces es importante para el manejo y sustentabilidad de las pesquerías y los ecosistemas marinos. Los sistemas remotos de video submarino con carnada (SRVSC) están entre las técnicas no destructivas más efectivas para el muestreo de peces óseos y elasmobranquios (tiburones, mantarrayas y rayas). Sin embargo, los SRVSC muestrean biota que es conspicua visiblemente; entonces, algunos taxones están mal muestreados o simplemente no se registran en los muestreos. Comparamos la diversidad de peces caracterizada usando SRVSC con la diversidad detectada por medio del metacódigo de barras de ADN ambiental (eDNA, en inglés). Muestreamos el agua de mar y capturamos imágenes con SRVSC en 48 localidades que incluyeron el arrecife y los pastos marinos dentro y fuera de una reserva marina (Bahía Jurien en el oeste de Australia). Se detectaron 83 géneros de peces de 13 órdenes, y la comunidad de peces descrita con el uso combinado del eDNA y el SRVSC produjo >30% riqueza más genérica que cuando cualquiera de los dos métodos se usó individualmente. En lugar de detectar una firma genética homogénea, los ensamblados de eDNA reflejaron la claridad espacial del SRVSC; la diferenciación de los taxones entre los pastos marinos y el arrecife fue clara a pesar la escala geográfica relativamente pequeña del sitio de estudio (~35 km²). Los taxones que no fueron muestreados por uno de los métodos, por causa de limitaciones y sesgos intrínsecos al método, casi siempre fueron detectados usando el otro método. Por lo tanto, el uso de SRVSC y el eDNA en concreto proporciona una visión más holística de las comunidades marinas de vertebrados en todos los hábitats. Ambos métodos son no invasivos, lo que incrementa su potencial para ser una implementación de uso amplio en la vigilancia de los ecosistemas marinos.

No fish have been found in the deepest 25% of the ocean (8,400—11,000 m). This apparent absence has been attributed to hydrostatic pressure, although direct evidence is wanting because of the lack of deepest-living species to study. The common osmolyte trimethylamine N-oxide (TMAO) stabilizes proteins against pressure and increases with depth, going from 40 to 261 mmol/kg in teleost fishes from 0 to 4,850 m. TMAO accumulation with depth results in increasing internal osmolality (typically 350 mOsmol/kg in shallow species compared with seawater's 1,100 mOsmol/kg). Preliminary extrapolation of osmolalities of predicted isosmotic state at 8,000—8,500 m may indicate a possible physiological limit, as greater depths would require reversal of osmotic gradients and, thus, osmoregulatory systems. We tested this prediction by capturing five of the second-deepest known fish, the hadal snailfish (Notoliparis kermadecensis; Liparidae), from 7,000 m in the Kermadec Trench. We found their muscles to have a TMAO content of 386 ± 18 mmol/kg and osmolality of 991 ± 22 mOsmol/kg. These data fit previous extrapolations and, combined with new osmolalities from bathyal and abyssal fishes, predict isosmotic state at 8,200 m. This is previously unidentified evidence that biochemistry could constrain the depth of a large, complex taxonomic group.