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To assess yellow eel (Anguilla anguilla L.) densities in non‐tidal waters, 1‐ha enclosure approach was developed. For unbiased density and biomass calculations, the catchability of the system needs to be evaluated. A telemetry study with 49 tagged eels was conducted in 2015 and 2016 to verify the effectiveness of the 1.8‐m high boundary net. Excluding recaptured eels (N = 10), 42.8% of the released eels (N = 15) escaped the enclosure within 48 hr. Regarding the movement frequency, similar movement patterns were observed for enclosed and escaped eels within 48 hr after release. Based on the telemetry study, it is concluded that the boundary net is recognised as an obstacle by yellow eels, and reduces the escapement of enclosed eels. [ABSTRACT FROM AUTHOR]

The miniaturization of acoustic transmitters enables researchers to tag smaller fish for telemetry studies, thus representing a greater proportion of the population of interest. Fish having a smaller transmitter burden (e.g., the weight of the transmitter relative to the weight of the fish) may also have fewer potential adverse transmitter effects. The development of an injectable acoustic transmitter has led to research that determined the least invasive and quickest method of implantation. Following that research, the objectives of this study were to determine the effects of transmitter implantation on swimming performance and predator avoidance, and to find a minimum size threshold of fish that can be tagged without adversely affecting those responses. To assess critical swimming speed ( U crit ; an index of prolonged swimming performance) and predator avoidance for juvenile Chinook Salmon ( Oncorhynchus tshawytscha ), fish were split into three treatments: (1) implantation with a dummy injectable acoustic transmitter (IAT treatment), (2) implantation with a dummy injectable acoustic transmitter and passive integrated transponder tag (IAT + PIT treatment), and (3) an untagged control. IAT treatment fish had lower U crit values than untagged controls among individuals below 79 mm fork length (transmitter burden 3.4–4.0%). U crit values for the IAT + PIT treatment were not significantly different from untagged controls and no size threshold was found. There was no significant difference in predator avoidance between fish implanted with the IAT or IAT + PIT compared to untagged controls. These guidelines could provide researchers and managers with a powerful tool to examine behavior and survival of small salmonids. [ABSTRACT FROM AUTHOR]

Overfishing is arguably the greatest ecological threat facing the oceans, yet catches of many highly migratory fishes including oceanic sharks remain largely unregulated with poor monitoring and data reporting. Oceanic shark conservation is hampered by basic knowledge gaps about where sharks aggregate across population ranges and precisely where they overlap with fishers. Using satellite tracking data from six shark species across the North Atlantic, we show that pelagic sharks occupy predictable habitat hotspots of high space use. Movement modeling showed sharks preferred habitats characterized by strong sea surface-temperature gradients (fronts) over other available habitats. However, simultaneous Global Positioning System (GPS) tracking of the entire Spanish and Portuguese longline-vessel fishing fleets show an 80% overlap of fished areas with hotspots, potentially increasing shark susceptibility to fishing exploitation. Regions of high overlap between oceanic tagged sharks and longliners included the North Atlantic Current/Labrador Current convergence zone and the Mid-Atlantic Ridge southwest of the Azores. In these main regions, and subareas within them, shark/vessel co-occurrence was spatially and temporally persistent between years, highlighting how broadly the fishing exploitation efficiently "tracks" oceanic sharks within their space-use hotspots year-round. Given this intense focus of longliners on shark hotspots, our study argues the need for international catch limits for pelagic sharks and identifies a future role of combining fine-scale fish and vessel telemetry to inform the ocean-scale management of fisheries. [ABSTRACT FROM AUTHOR]

Tournament displacement, stockpiling near release points, and handling stress are major concerns for managers of sport fisheries in the southeastern USA. We examined the effects of transport distance and tournament handling stress on dispersal of 40 Largemouth BassMicropterus salmoidesvia telemetry from May 2012 to September 2013 in the Albemarle Sound system of eastern North Carolina. Largemouth Bass were captured from four tributaries of Albemarle Sound and transported 16.5–45 km to a central release point before being acoustically tagged and released. Movement data from an array of passive receivers was used to calculate rates of dispersal from the release point, emigration from the study area and return to capture location over time. Blood cortisol concentration, collected from our tagged Largemouth Bass and those captured in an actual tournament, was used to determine the effect of stress on potential postrelease movement and survival. Our findings indicate little evidence of long-term stockpiling (i.e., fish remaining close to release point; Richardson-Heft et al. 2000); 57% of displaced Largemouth Bass dispersed more than 500 m from the release point within 7 d and 87% within 21 d postrelease. Half of those that emigrated from Edenton Bay returned to their capture location. However, no Largemouth Bass displaced 35–45 km returned to their capture locations, suggesting that long-distance displacement inhibits return. Fishing (2.8%) and nonharvest mortality (0.5%) were low throughout this study except for peaks observed during late spring (42.9%) and early summer (25.1%) of 2013. Mean cortisol concentrations were similar in Largemouth Bass collected during our simulated tournament (126.7 ng/mL) and an actual tournament (118.4 ng/mL). However, cortisol concentrations were unrelated to survival, postrelease dispersal, or return of tagged individuals to their capture location. Largemouth Bass appear to be able to cope with current tournament practices; however, restrictions on displacement distance may increase return rates. Received August 26, 2014; accepted January 14, 2015 [ABSTRACT FROM PUBLISHER]