Seasonal movement of the American horseshoe crab Limulus polyphemus in a semi-enclosed bay on Cape Cod, Massachusetts (USA) as determined by acoustic telemetry

摘要

American horseshoe crabs Limulus polyphemus were tracked using acoustic telemetry and traditional tagging in asemi-enclosed bay on Cape Cod (Pleasant Bay),Massachusetts,USA,to determine seasonal movement patterns.Fifty-five activelyspawning females were fitted with transmitters in 2008 and 2009 and were tracked using acoustic telemetry from May 2008through July 2010.Fifteen crabs with transmitters also had archive depth-temperature tags attached.In addition,over 2000spawning crabs (males and females) were tagged with US Fish and Wildlife (USFWS) button tags over the same period.Ninety-one percent of the crabs with transmitters were detected during this study.In the spring,crabs were primarily located inthe northern section of the bay near spawning beaches,whereas in the fall crabs moved towards the deeper portions of the bay,and some may have overwintered in the bay.There was evidence that a majority (58%-71%) of the females with transmittersspawned in two sequential seasons.One archive tag was recovered resulting in a year-long continuous record of depth and temperaturedata that,when integrated with telemetry data,indicated that the crab overwintered in the bay.The live recapture rate ofcrabs with USFWS button tags was 11%,with all re-sighted crabs except one observed inside Pleasant Bay.Eighty-three percentof recaptures were found within 2.5km of the tagging location,and 51% were observed at the same beach where they were tagged.This study provides further evidence that horseshoe crabs in Pleasant Bay may be philopatric to this