Would you sleep in a graveyard? Assessing queen conch’s behavioral response to knocked shells

Presented by Claire Thomas

Claire Thomas and Oliver Dodd

Queen conch are in decline throughout most of their range, including in The Bahamas. Overfishing and the harvest of juvenile conch are clear contributors to the decline in Bahamian stock, but there is a prevailing idea among local fishermen in The Bahamas that queen conch are moving away from knocked shells that are tossed overboard at sea by fishermen. With a keen sense of smell and good eyesight, there is reason to believe that conch may be affected by exposure to knocked shells. To address this issue, a laboratory-based experiment was designed to determine if conch change their behavior (e.g., exhibit “avoidance” behaviors) due to the presence of a knocked shell. Conch were collected in South Eleuthera, acclimated in tanks at the Cape Eleuthera Institute wet lab, and then exposed to one of three treatments: a rock (control), an old knocked shell (potential visual cue) and a freshly knocked shell (potential visual and chemical cues). Their behavior and location within the tanks was then monitored for 4 hours, to quantify potential avoidance of the treatment object. Preliminary analysis of the lab trials shows that although avoidance behavior was observed, it was not the predominant response, and there was no significant effect of treatment object on behavior. With declines noted on several family islands, urgent changes in management are necessary to ensure the health of future conch populations. Disposal of knocked shells may influence current conch populations, and laws regulating shell disposal may benefit the conch. Conversely, if conch are unaffected by knocked shells, this information may be aggressively relayed to fishing communities on the family islands, and closer attention can be paid to management strategies that address the current fishing pressure, and not on shell disposal.