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Skates (class Chondrichthyes; subclass Elasmobranchii; order Rajiformes; family Rajidae) comprise one quarter of extant chondrichthyans, yet have received little attention in the scientific literature likely due to their relatively low economic value and difficulties in species identification. The absence of species‐specific information on catch, life history and migration of skates has often precluded the development of single‐species stock assessments and led to the use of cursory multispecies assessments, which lack the ability to track species‐specific catch and abundance trends. This has resulted in undetected local extirpations, as has been previously reported for common (Dipturus batis, Rajidae), white (Rostroraja alba, Rajidae) and long‐nose (Dipturus oxyrhinchus, Rajidae) skates in the Irish Sea. Here, we (a) use case studies to illustrate how the perception of skate population structure and stock status has historically been masked through multispecies assessment and management practices, (b) review current information on the movement of skates and identify gaps in knowledge, and (c) identify biases associated with the use of various tagging technologies, which have confounded our understanding of movement and migration ecology of skates. Considering that over 40% of extant Rajidae species are listed as “Data Deficient” by the International Union for Conservation of Nature, we illustrate a critical need to broaden the current understanding of skate life history, movement and migration ecology by providing recommendations on the further application of electronic tags and biogeochemical natural tags in movement studies and highlight the benefits that studies using these approaches have for novel management frameworks.

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Despite the ecological and economic importance of the Caribbean reef shark (Carcharhinus perezi), little data exist regarding the movements and habitat use of this predator across its range. We deployed 11 pop-up satellite archival tags on Caribbean reef sharks captured in the northeast Exuma Sound, The Bahamas, to assess their horizontal and vertical movements throughout the water column. Sharks showed high site fidelity to The Bahamas suggesting Bahamian subpopulations remain protected within the Bahamian Shark Sanctuary. Depth data indicate that Caribbean reef sharks spent a significant proportion (72–91%) of their time above 50 m in narrow vertical depth bands, which varied considerably on an individual basis. This may be indicative of high site fidelity to specific bathymetric features. Animals exhibited three broadly categorized sporadic off-bank excursions (more than 50 m excursions) down to a depth of 436.1 m, which were more frequent during the night. These deeper excursions during night may be indicative of foraging in relation to prey on mesophotic reefs, as well as diel-vertically migrating prey from the deeper meso- and bathypelagic zones. These vertical movements suggest that Caribbean reef sharks can be significant vectors of ecosystem connectivity further warranting holistic multi-system management and conservation approaches.

Newcastle University ePrints -eprint.ncl.ac.uk Shipley ON, Olin JA, Polunin NVC, Sweeting CJ, Newman SP, Brooks EJ, Barker S, Witt MJ, Talwar B, Hussey NE. Polar compounds preclude mathematical lipid correction of carbon stable isotopes in deep-water sharks. Abstract 30Lipids affect isotope values in marine fishes, however such effects remain poorly 31 described for many extant shark taxa, especially deep-sea species. Here we report the effects 32 of lipid extraction (LE) on δ 13 C, δ 15 N, and C:N values of seven deep-sea sharks, generate 33 novel mathematical normalizations for δ 13 C based on the relationship between bulk and lipid 34 extracted values (δ 13 CBulk and δ 13 CLE)., and examine whether common normalized correction 35 models provide a robust method for addressing lipid-biasing effects in two species, the Cuban 36 dogfish (Squalus cubensis; n = 20), and Greenland shark (Somniosus microcephalus; n = 24). 37 LE generally resulted in an isotopic enrichment of 13 C and 15 N, but produced variable effects 38 on C:N across all species. Novel mathematical normalizations for δ 13 C were derived from the 39 pooled shark community, and a single species-specific correction was generated for the 40 Cuban dogfish, but could not be determined for the Greenland shark. Four common lipid 41 correction models used for teleosts, failed to accurately predict δ 13 C values statistically 42 similar to δ 13 CLE, in both Cuban dogfish and Greenland sharks, likely due to the confounding 43 effects of lipids and urea on C:N. These observations suggest that chemical lipid extraction 44 should be a mandatory procedure prior to interpreting stable isotope data for deep-sea sharks, 45 at least for those species where lipid effects are large. 46 47

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Birds, mammals, and certain fishes, including tunas, opahs and lamnid sharks, are endothermic, conserving internally generated, metabolic heat to maintain body or tissue temperatures above that of the environment. Bluefin tunas are commercially important fishes worldwide, and some populations are threatened. They are renowned for their endothermy, maintaining elevated temperatures of the oxidative locomotor muscle, viscera, brain and eyes, and occupying cold, productive high-latitude waters. Less cold-tolerant tunas, such as yellowfin tuna, by contrast, remain in warm-temperate to tropical waters year-round, reproducing more rapidly than most temperate bluefin tuna populations, providing resiliency in the face of large-scale industrial fisheries. Despite the importance of these traits to not only fisheries but also habitat utilization and responses to climate change, little is known of the genetic processes underlying the diversification of tunas. In collecting and analyzing sequence data across 29,556 genes, we found that parallel selection on standing genetic variation is associated with the evolution of endothermy in bluefin tunas. This includes two shared substitutions in genes encoding glycerol-3 phosphate dehydrogenase, an enzyme that contributes to thermogenesis in bumblebees and mammals, as well as four genes involved in the Krebs cycle, oxidative phosphorylation, β-oxidation, and superoxide removal. Using phylogenetic techniques, we further illustrate that the eight Thunnus species are genetically distinct, but found evidence of mitochondrial genome introgression across two species. Phylogeny-based metrics highlight conservation needs for some of these species.