Effects of holding temperature and handling stress on the upper thermal tolerance of threadfin shad Dorosoma petenense.

The critical thermal maxima (T(MAX)) of threadfin shad Dorosoma petenense exposed to standardized stress (30 s handling in a dip-net), simulating stressors endured during fish loading before transport, were measured over a range of holding temperatures (15, 20 and 25 degrees C). Dorosoma petenense T(MAX) showed a significant thermal effect, displaying mean +/-s.d. critical thermal maxima of 26.5 +/- 1.6, 30.9 +/- 1.2 and 33.3 +/- 1.4 degrees C, when tested at temperatures of 15, 20 and 25 degrees C, respectively. Dorosoma petenense T(MAX) levels were also affected by stress, with handled fish showing significantly lower values than control fish exposed to 15 (mean +/-S.D. T(MAX) = 25.6 +/- 2.0 degrees C), 20 (27.6 +/- 2.8 degrees C) and 25 degrees C (32.0 +/- 2.6 degrees C). In addition to providing basic information on D. petenense thermal tolerance, experimental results suggest that fishery managers should consider the whole suite of potential stressors, such as air exposure during handling and fish loading, when developing management criteria.