Publication date: November 2019
Source: Journal of Experimental Marine Biology and Ecology, Volume 520
Author(s): James D. Salierno, Andrew S. KaneAbstract
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 < .01), NND decreased (p < .05), and the number of conspecific interactions increased (p < .10). In contrast, STX-exposed fish showed suppressed shoaling dynamics during late exposure observations (T90–120 min), where shoaling time decreased (p < .10), NND and NNA increased (p < .05), and the number of conspecific interactions decreased (p < .05). Recovery observations taken 24-h after PbTx- and STX-exposure, revealed groups of fish with suppressed shoaling dynamics including reduced group cohesiveness. Groups of fish post-exposure spent less time shoaling (p < .05) with greater NND (p < .10) and fewer conspecific interactions (p < .10). STX-exposed fish also had greater NNA (p < .01). PbTx-exposed fish spent more time sedentary while remaining in groups (p < .05) and more time solitary (p < .05). Results indicate that exposure to environmentally relevant concentrations of PbTx and STX have demonstrable effects on mummichog shoaling and group behaviors. Behavioral responses observed during HAB toxin exposure may be associated with the excitatory action of PbTx and the paralytic effects of STX. Post-exposure outcomes indicate impacted shoaling dynamics and group behaviors. Such changes are associated with reduced foraging capacity and predator vigilance, thus facilitating toxin trophic transfer, and ultimately decreasing survival for exposed killifish.