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Iteroparity occurs when organisms reproduce more than once, and is seen as a bet-hedging reproductive strategy. Despite a wealth of research on iteroparous Atlantic salmon, steelhead, brown trout, and Arctic charr, the determinants of reproductive investment, the intra- and interspecific differences in the degree of iteroparity, the drivers of repeat spawning, and the contribution of repeat spawners to populations and sustainability remain unclear. In particular, the knowledge base is stronger for Atlantic salmon and brown trout, but relatively weak for Arctic charr and steelhead. While juveniles, maiden spawners and repeat spawners are facing similar challenges, many threats specific to the kelt stage are emerging (e.g., downstream migration passed barriers after spawning). Recent work has quantified the benefits of iteroparity for population resilience, and the potential for iteroparity to increase when anthropogenic stressors are mitigated. This is the first literature review paper synthetizing the growing knowledge base that exists on various aspects of the ecology and biology of repeat spawners in freshwater and at sea, the threats they face, the proximate and ultimate mechanisms underlying iteroparity in salmonids, the importance of iteroparity for population-level processes, as well as highlighting pressing areas of research. Collectively, this work offers a valuable resource to fisheries scientists and managers by shedding light on an important life-history stage that warrants more attention to mitigate these threats and restore healthy wild salmonid populations.

\"All young children love to play in the waves at the beach. Now here's a Hello, World! board book that teaches them all about oceans and the creatures and plants that live there.\"-- Publisher's description.

With about 8000 marine benthic species, the amphipod crustaceans form one of the richest animal groups of the worldwide Ocean. They have colonized a wide range of soft- and hard-bottom natural and artificial habitats extending from the intertidal to hadal zones. Moreover, they show a broad size spectrum, with numerous giant species exceeding 20 cm in length and some species smaller than 2 mm. When biofouling artificial hard surfaces, some tube-building species can form very dense populations comprising up to 100,000 individuals per square meter. Amphipods are important prey for fish and mammals. Along with cephalopod juveniles, they are also included in the trophic diet of shorebirds that consume amphipods mostly during the low tide on tidal flats. They display diel migration, which reinforces the predation by demersal fish in the suprabenthic zone just above the sea bed, as well as by pelagic fish in the water column. Despite their importance in terms of biodiversity and trophic transfer, no general overview is available on the role of benthic amphipods in marine ecosystem food webs. Various methods, including laboratory and field experiments, as well as the analysis of stomach contents and DNA extraction, have been used to identify the prey/predator trophic links. Based on an extensive literature review, this study discusses the role of marine benthic amphipods as potential food for higher trophic levels in natural and artificial hard-bottom communities created via the construction of offshore wind farms.

Readers take a dive underwater to take an in-depth look at the mechanics behind fish and other sea creatures.

Background Shallow nearshore marine ecosystems are changing at an increasing rate due to a range of human activities such as urbanisation and commercial development. As a result, an increasing number of structural modifications occur in coastal nursery and spawning habitats of fish. Concomitant to this increase, there have been declines in many coastal fish populations and changes in the composition of fish communities. As requested by Swedish stakeholders, this review aimed to synthesise scientific evidence of the impact on fish recruitment of structural modifications in temperate coastal areas. Methods We searched for peer-reviewed and grey literature on such impacts in English, Dutch, Danish, Finnish, German, Swedish and Spanish. Searches were performed in bibliographic databases, specialist websites, bibliographies of review articles. We also contacted stakeholder to find relevant literature. Eligible studies included small- and large-scale field studies in marine systems and large lakes (> 10,000 km 2 ) in temperate regions of the Northern and Southern Hemispheres. Included replicated comparisons of fish recruitment between altered and unaltered control areas, comparisons before and after an alteration, or both. Relevant outcomes (response variables) included measures of recruitment defined as abundance of juvenile fish in coastal habitats. All fish species were considered. Articles were screened for eligibility by title, abstract and full text. Eligible studies were critically appraised based on their external and internal validity. From each eligible study of sufficient validity, we extracted information on study design, measured outcomes, exposure, type of comparator, effect modifiers and study findings. Study findings were synthesised narratively. Results We searched for eligible studies in 15 databases, 24 specialist websites, Google Scholar, and bibliographies of 11 review articles. The review finally included 37 studies that were eligible and of sufficient validity to be considered for final synthesis. Most studies (23 of 37) were from the Northern Hemisphere. Studies varied in design, spatial resolution, target fish species, and type of structural habitat change. This high level of variation did not allow for a quantitative synthesis and prevented us from drawing general conclusions on the impact of structures or structural modifications on fish recruitment. In this review we provide a narrative synthesis of the evidence base and classify eligible studies into six categories (based on type of exposure and comparator). The categories are as follows: the impacts on fish recruitment of: (1) artificial structures in coastal areas, (2) structures designed as fish attractors, (3) large scale urban sprawl, (4) ‘novel’ habitats, (5) habitat loss, and (6) restoration. Conclusions This review revealed a very limited evidence base for how structural modifications and marine urban sprawl can affect fish recruitment. Thus, there is a substantial mismatch between stakeholder needs and research evidence. Further, the impact and ecological performance of artificial structures depend both on context and species. Clearly, there is a need for more research on the subject, especially on long-term consequences at larger spatial scales.

Explores the plants, animals, and ecology of oceans and seas. Includes 25 science projects and links to online resources.

Abstract With the unprecedented environmental changes caused by climate change including ocean acidification, it has become crucial to understand the responses and adaptive capacity of fish to better predict directional changes in the ecological landscape of the future. We conducted a systematic literature review to examine if simulated ocean acidification (sOA) could influence growth and reproduction in fish within the dynamic energy budget theory framework. As such, we chose to examine metabolic rate, locomotion, food assimilation and growth in early life stages (i.e. larvae and juvenile) and adults. Our goal was to evaluate if acclimatization to sOA has any directional changes in these traits and to explore potential implications for energetic trade-offs in these for growth and reproduction. We found that sOA had negligible effects on energetic expenditure for maintenance and aerobic metabolism due to the robust physiological capacity regulating acid–base and ion perturbations but substantive effects on locomotion, food assimilation and growth. We demonstrated evidence that sOA significantly reduced growth performance of fish in early life stages, which may have resulted from reduced food intake and digestion efficiency. Also, our results showed that sOA may enhance reproduction with increased numbers of offspring although this may come at the cost of altered reproductive behaviours or offspring fitness. While these results indicate evidence for changes in energy budgets because of physiological acclimatization to sOA, the heterogeneity of results in the literature suggests that physiological and neural mechanisms need to be clearly elucidated in future studies. Lastly, most studies on sOA have been conducted on early life stages, which necessitates that more studies should be conducted on adults to understand reproductive success and thus better predict cohort and population dynamics under ongoing climate change. Lay Summary Ocean acidification (OA) could alter energy budgets of marine fish. OA had negligible effects on aerobic metabolism, but substantive effects on locomotion, food assimilation and growth, suggesting a potential shift in energy budgets in the future. Also, OA may enhance reproduction potentially at the cost of altered reproductive behaviours or offspring fitness.

Traveling from the rock pools of the shoreline to the deepest depths of the ocean, a blending of illustrations and facts about marine animals provides an introduction to some of the ocean's rarely seen creatures.

The Straits of Florida comprise an important migratory route for apex predators moving among the Gulf of Mexico, Atlantic Ocean, and Caribbean Sea. Off Cuba’s northwestern coast, various gear types are used by Cuban fishers, including small‐scale pelagic longlines. We report here the results of a 2011–2019 monitoring program for the longline fleet based in Cojímar, Cuba. This fleet comprises 134 small vessels targeting mostly swordfish (family Xiphiidae), billfishes (family Istiophoridae), tunas (family Scombridae), and sharks (class Chondrichthyes) within 20 km of Cuba’s coast. Most operations are nocturnal with 11–12‐h sets comprising an average of 56 hooks on 6,643 m of mainline. Five orders, eight families, and 18 species of sharks were documented in this fishery. Two carcharhinids (Silky Shark Carcharhinus falciformis and Oceanic Whitetip Shark C. longimanus) and two lamnids (Longfin Mako Isurus paucus and Shortfin Mako I. oxyrinchus) were the most abundant shark species caught, with shark CPUE averaging 1.98 sharks/trip (SD = 0.938). Catch abundance showed seasonal differences, with Silky Sharks and Longfin Makos more common in winter and Oceanic Whitetip Sharks more common in summer and autumn. Bimodal size structure in some species suggests multiple life stages utilizing the area, while the predominance of young sharks in species including the Oceanic Whitetip Shark suggests the importance of the area as juvenile habitat, possibly as a pupping and/or nursery ground. This characterization of the Cuban longline fishery is an important step forward for Cuba’s National Plan of Action for Sharks and demonstrates the potential impacts that small‐scale fisheries can have on vulnerable sharks.