Short‐term survival and movements of Atlantic sharpnose sharks captured by hook‐and‐line in the north‐east Gulf of Mexico

Abstract

Ultrasonic telemetry was used to compare post‐release survival and movements of Atlantic sharpnose sharks Rhizoprionodon terraenovae in a coastal area of the north‐east Gulf of Mexico. Ten fish were caught with standardized hook‐and‐line gear during June to October 1999. Atlantic sharpnose sharks were continuously tracked after release for periods of 0·75 to 5·90 h and their positions recorded at a median interval of 9 min. Individual rate of movement was the mean of all distance and time measurements for each fish. Mean ± s.e. individual rate of movement was 0·45 ± 0·06 total lengths per second (LT s−1) and ranged from 0·28 to 0·92 LT s−1 over all fish. Movement patterns did not differ between jaw and internally hooked Atlantic sharpnose sharks. Individual rate of movement was inversely correlated with bottom water temperature at capture (r2 = 0·52, P ≤ 0·05). No consistent direction in movement was detected for Atlantic sharpnose sharks after release, except that they avoided movement towards shallower areas. Capture‐release survival was high (90%), with only one fish not surviving, i.e. this particular fish stopped movement for a period of 10 min. Total rate of movement was total distance over total time (m min−1) for each Atlantic sharpnose shark. Mean total rate of movement was significantly higher immediately after release at 21·5 m min−1 over the first 1·5 h of tracking, then decreased to 11·2 m min−1 over 1·5–6 h, and 7·7 m min−1 over 3–6 h (P ≤ 0·002), which suggested initial post‐release stress but quick recovery from capture. Thus, high survival (90%) and quick recovery indicate that the practice of catch‐and‐release would be a viable method to reduce capture mortality for R. terraenovae.