Observations on spiny dogfish (Squalus acanthias) captured in late spring in a North Carolina estuary

Abstract

Five spiny dogfish were captured in early-mid May during gillnet and longline sampling targeting juvenile coastal sharks in inshore North Carolina waters. Dogfish captures were made within Back Sound and Core Sound, North Carolina. All dogfish were females over the size at maturity, and were caught at stations 1.77-2.74 m in depth, with temperatures 22.9-24.2 °C, 32.8-33.4 ppt salinity, and 6.9-8.0 mg/L dissolved oxygen. Stations where dogfish were captured were approximately 6.5-15.7 km from the nearest inlet and 43.4-247.1 m from the nearest seagrass bed. These observations are among the latest in the spring for spiny dogfish in the southeastern U.S. and occurred at higher temperatures than previously recorded for this species. It is unclear whether late-occurring spiny dogfish in this area represent a cryptic late-migrating or resident segment of the Northwest Atlantic population.

Differential Effects of Temperature on Oxygen Consumption and Branchial Fluxes of Urea, Ammonia, and Water in the Dogfish Shark (Squalus acanthias suckleyi)

“…A temperature of 227C is likely close to the upper critical temperature (C t max ) of Squalus acanthias suckleyi, at least without prior acclimation, because most of the present animals lost orientation, turning laterally or completely over during this treatment. Note, however, that they have been caught in the wild at 247C (Bangley and Rulifson 2014). In order to test the hypothesis that gill permeability increases because dogfish become oxygen limited at 227C, sharks were exposed to this high temperature (227C) in the presence of hyperoxia (PO 2 > 309 Torr) and compared with fish maintained at the control temperature (127C) but also exposed to hyperoxia.…”

“…Ammonia, urea-N, and tritiated water ( 3 H 2 O) fluxes were assessed following exposure to 7.57, 127 (acclimation temperature, used as control), 157, 187, and 227C. Based on fishery data and capture records, this temperature range is environmentally relevant for this species that occurs between extremes of 47 and 247C in the wild (Bangley and Rulifson 2014;Sagarese et al 2014). Our general hypothesis was that as metabolic demand for oxygen increased with temperature, the fluxes of ammonia, urea-N, and 3 H 2 O at the gill would increase in parallel with that of oxygen.…”