Brevetoxin and saxitoxin alter shoaling dynamics in mummichog, Fundulus heteroclitus

Abstract Shoaling and social behaviors of Fundulus heteroclitus (mummichog, an estuarine killifish) were observed in response to harmful algal bloom (HAB) neurotoxin exposures. Six replicate groups of 5 fish were videographed pre-exposure, during a sublethal 2-h exposure to brevetoxin, PbTx-2 (PbTx, 40 and 55 ppb) or saxitoxin (STX,100 and 150 ppb) at the beginning (T0–30min) and at the end (T90–120 min) of the exposure period, and during recovery, 24-h post-exposure. Fish shoaling and social behaviors, including nearest neighbor angle (NNA) and nearest neighbor distance (NND) between fish, solitary and sedentary time, and number of conspecific interactions, were quantified and analyzed using customized software. There was no difference in shoaling behavior outcomes between the PbTx or STX “high” and “low” concentrations within observation times (p > .26). Exposure and post-exposure group outcomes were compared to pre-exposure (baseline) observations using repeated measures. PbTx- and STX-exposed fish showed altered shoaling behaviors during- and post-exposure, compared to pre-exposure baseline observations. PbTx-exposed fish showed heightened shoaling dynamics during early exposure observations (T0–30), where shoaling time increased (p