Timing of the reproductive cycle of waved whelk, Buccinum undatum, on the U.S. Mid-Atlantic Bight

Abstract

Development of the unmanaged waved whelk (Buccinum undatum) fishery on the Mid-Atlantic continental shelf of the United States has initiated investigation into fisheries-related biological and population attributes of the species in this region. Maturation and reproduction timing vary by location for this species and are likely linked to bottom water temperature. This study examined the seasonal fluctuations in relevant body metrics and gonadosomatic index in relation to bottom temperature to assess the timing of the reproductive cycle of the B. undatum population in the southern-most extent of this species’ range in the Atlantic. To characterize variation over the maturation schedule, nine locations in the Mid-Atlantic Bight (MAB) were sampled five times between January 2017 and September 2017. Maturity was assessed macroscopically, with morphological methods, and via gonadosomatic indices. Male behavioral maturity estimates, based on a penis length to shell length index (PL50), were compared to estimates made using other methods for assessing maturity to test the efficacy of this commonly used ratio. Mature whelk were found in all months and peak reproductive activity was observed in spring and early summer. This timing suggests that ideal sampling to visually identify maturity to estimate size of maturity would be late winter or early spring. Unique oceanographic dynamics in the MAB, such as strong seasonal stratification results in large changes in annual bottom temperature which appears to be closely linked to the reproductive cycle in this region. Our data suggest that B. undatum in the MAB experience spawning and development at ~ 7–8 °C; temperatures warmer than Canadian populations and cooler than some UK conspecifics. To our knowledge, this is the first study to document the annual reproductive cycle of waved whelk in the United States.