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Sepulveda C.A.,Pfleger Institute of Environmental Research PIER | Heberer C.,National Oceanic and Atmospheric Administration | Aalbers S.A.,Pfleger Institute of Environmental Research PIER | Spear N.,Southwest Fisheries Science Center | And 3 more authors.
Fisheries Research | Year: 2015

The common thresher shark (Alopias vulpinus) is the focus of a popular southern California recreational fishery that targets individuals using multiple fishing gears and techniques. Despite increasing trends in the use of catch and release techniques in the recreational fishery for thresher sharks, a comprehensive estimate of post-release survival is not available for all modes of capture. This study focused on assessing post-release survival in two modes of capture routinely observed in the southern California recreational fishery: (1) sharks that are caught using caudal-based angling techniques and unintentionally released with trailing gear left embedded and (2) sharks that are caught and released using mouth-based angling techniques. Post-release survivorship was assessed using pop-up satellite archival tags programed for 10- and 90-day deployments, with the former used for mouth-caught sharks and the latter for individuals with trailing gear. Post-release survivorship estimates for the trailing gear studies were based on data from nine common thresher sharks (111-175. cm FL) while the mouth-based experiments utilized data from an additional seven sharks (125-187. cm fork length, FL). For the trailing gear studies, six sharks died within 5. days after release, one died after 81. days, and two sharks survived the deployment period for an overall survivorship rate of 22%. All seven mouth-hooked common thresher sharks survived the acute (~10. days) effects of capture (100% survivorship). These results suggest that in the southern California recreational thresher shark fishery, caudal-based angling techniques, which often result in trailing gear left embedded in the shark, can negatively affect post-release survivorship. This work also reveals that mouth-based angling techniques can, when performed properly, result in high survivorship of released sharks. © 2014 Elsevier B.V. Source

Heberer C.,National Oceanic and Atmospheric Administration | Aalbers S.A.,Pfleger Institute of Environmental Research PIER | Bernal D.,University of Massachusetts Dartmouth | Kohin S.,Southwest Fisheries Science Center | And 2 more authors.
Fisheries Research | Year: 2010

The common thresher shark Alopias vulpinus) is the focus of a popular southern California recreational fishery that typically captures individuals by hooking them in the caudal fin. This technique reduces the ability for forward locomotion and the capacity for ram ventilation. This study assessed the post-capture survivorship of tail-hooked adult and sub-adult common thresher sharks using pop-up satellite archival tags (PSATs) and quantified physiological indicators of capture stress in the blood. Survival of the acute effects of capture was determined from the depth and temperature records of 10-day PSAT deployments. Survivorship estimates were based on 19 common thresher sharks [160-221. cm fork length (FL); ∼67-151. kg] captured in southern California from 2007 to 2009 using recreational stand-up tackle (36. kg). Five mortalities were observed over the course of the study resulting in an overall post-release mortality estimate of 26%. All mortalities occurred in large individuals (≥180. cm FL) with fight times ≥85. min. The archived depth and temperature data from surviving sharks resembled those of previous common thresher movement studies with a diel depth distribution predominantly within the uniformed temperature surface layer. Capture induced stress parameters measured from the blood of eight additional common thresher sharks that were not tagged revealed plasma lactate and hematocrit levels that were significantly elevated with increased fight time. Similarly, all thresher sharks showed heightened heat shock protein 70 hsp 70) values relative to those obtained from blood that was allowed to recover in vitro for 24. h. Collectively, our findings indicate that large tail-hooked common thresher sharks with prolonged fight times (≥85. min) exhibit a heightened stress response which may contribute to an increased mortality rate. These results suggest that for larger individuals the current caudal-based capture methods used in the California recreational fishery may not be suitable for an effective catch-and-release based conservation strategy. © 2010 Elsevier B.V. Source

Aalbers S.A.,Pfleger Institute of Environmental Research PIER | Sepulveda C.A.,Pfleger Institute of Environmental Research PIER
Journal of Fish Biology | Year: 2012

This study reports the use of a long-term acoustic recording system (LARS) to remotely monitor white seabass Atractoscion nobilis spawning sounds at three sites along the southern California coastline, adjacent to Camp Pendleton. On the basis of previous studies of A. nobilis sound production relative to periods of known spawning activity, LARS were set to continuously record ambient sounds for a 2 h period around sunset from April to June 2009. Acoustic analyses identified A. nobilis courtship sounds on 89, 28 and 45% of the days at the three locations, respectively. From 474 h of acoustic data, spawning-related sounds (chants) were detected on 19 occasions in 2009 with an additional 11 spawning chants recorded during a 2007 validation period. Most spawning chants occurred within 30 min of sunset during the months of May and June at a mean ±s.d. surface temperature of 18·2 ± 1·2° C. Consecutive daily spawning activity was not apparent at any sites in 2009. Atractoscion nobilis spawning chants were recorded at all three sites, suggesting that shallow rocky reefs which support kelp forests provide suitable A. nobilis spawning habitat. Results confirm the utility of passive acoustic recorders for identifying A. nobilis spawning periods and locations. © 2012 The Authors. Journal of Fish Biology © 2012 The Fisheries Society of the British Isles. Source

Romo-Curiel A.E.,CICESE | Herzka S.Z.,CICESE | Sosa-Nishizaki O.,CICESE | Sepulveda C.A.,Pfleger Institute of Environmental Research PIER | Aalbers S.A.,Pfleger Institute of Environmental Research PIER
Fisheries Research | Year: 2015

White Seabass (Atractoscion nobilis; Sciaenidae) comprise an important commercial resource in the USA and Mexico, but there are few growth rate estimates and its population structure remains uncertain. Growth rates were estimated based on otolith analysis of fish collected at three locations spanning 1000-km. Variations in growth rates were assessed at the population level and by reconstructing individual growth trajectories. Seabass were sampled from fisheries operating off southern California (SC) and the northern and southern (NBC and SBC) Baja California peninsula from 2009 to 2012 (n=415). Ages ranged from 0 to 28-years, but fish >21-years of age were sampled infrequently. Size-at-age was highly variable, particularly for fish <5-years. White Seabass grew quickly during the first 8-years of life after which growth rates decreased considerably. Fitting the size-at-age data with the von Bertalanffy growth function and applying the likelihood ratio test to parameter estimates indicated that SC, NBC and SBC did not differ significantly in growth rates (0.18-0.19-yr-1) or asymptotic length (141-cm total length). Individual otolith growth trajectories showed high variability within regions and there were only significant differences in the average width of the first annuli. However, residual analysis of the average annual radii suggests fish from SBC had a larger size-at-age. Those differences may be related to the higher coastal temperatures found in southern coastal waters. Although growth rates may differ during the first year of life, findings suggest growth to be similar across the study range. © 2014 Elsevier B.V. Source

Romo-Curiel A.E.,CICESE | Herzka S.Z.,CICESE | Sepulveda C.A.,Pfleger Institute of Environmental Research PIER | Perez-Brunius P.,Pfleger Institute of Environmental Research PIER | Aalbers S.A.,Pfleger Institute of Environmental Research PIER
Estuarine, Coastal and Shelf Science | Year: 2016

White seabass, Atractoscion nobilis, is an important coastal resource throughout both California and Baja California, but whether this species comprises a single or multiple subpopulations in the northeastern Pacific is not known. The aim of this study was to infer larval rearing habitats and population structure of white seabass by sampling adults from three regions spanning a latitudinal temperature gradient and a distance of over 1000 km, and analyzing the isotopic composition (δ18O and δ13C) of otolith aragonite corresponding to the larval, juvenile and adult stages. Otolith cores revealed high isotopic variability and no significant differences among regions, suggesting overlapping rearing conditions during the larval stage, the potential for long distance dispersal or migration or selective mortality of larvae at higher temperatures. Back-calculated temperatures of aragonite precipitation derived using regional salinity-δw relationships and local salinity estimates also did not differ significantly. However, there were significant differences between the δ18O values of the first seasonal growth ring of age 0 fish as well as back-calculated aragonite precipitation temperatures, suggesting the presence of two potentially discrete subpopulations divided by Punta Eugenia (27°N) along the central Baja California peninsula. These findings are consistent with regional oceanographic patterns and are critical for understanding white seabass population structure, and provide information needed for the implementation of appropriate management strategies. © 2016 Elsevier Ltd. Source

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