Age, size, and sexual maturity of channeled whelk (Busycotypus canaliculatus) in Buzzards Bay, Massachusetts

Abstract

Abstract-With the southern NewEngland lobster fishery in distress, lobster fishermen have focused more effort toward harvesting channeled whelk (Busycotypus canaliculatus). However, minimal research has been conducted on the life history and growth rates of channeled whelk. Melongenid whelks generally grow slowly and mature late in life, a characteristic that can make them vulnerable to overfishing as fishing pressure increases. We sampled channeled whelk from Buzzards Bay, Massachusetts, in August 2010 and in July 2011, studied their gonad development by histology, and aged them by examining opercula. Males had a slower growth rate and a lower maximum size than females. Male whelk reached 50% maturity (SM 50 ) at 115.5 mm shell length (SL) and at the age of 6.9 years. Female whelk reached SM 50 at 155.3 mm SL and at the age of 8.6 years. With a minimum size limit of 69.9 mm (2.75 in) in shell width, males entered the fishery at 7.5 years, a few months after SM 50 , but females entered the fishery at 6.3 years, approximately 2 years before SM 50 . Increased fishing pressure combined with slow growth rates and the inability to reproduce before being harvested can easily constrain the long-term viability of the channeled whelk fishery in Massachusetts.

Sex Differences in Growth of Channeled Whelks from Buzzards Bay, Massachusetts, during One or Two Years at Liberty

“…Traps were allowed to soak for 1 week and then were retrieved weekly over a 4-week period in each year. Sites sampled in 2010 were mostly located in eastern Buzzards Bay, whereas those sampled in 2011 were mostly in the western portion of the bay (see Peemoeller and Stevens 2013 for descriptions of the~30 capture locations). Whelks from different sites were pooled; therefore, water temperatures at individual sites were not measured, but we did examine seawater temperature data from National Oceanic and Atmospheric Administration (NOAA) data buoy station BZBM3 located at the NOAA Northeast Fisheries Science Center dock in Woods Hole, Massachusetts (Figure 1; NOAA station 8447930; www.…”

“…35-4.66 in). However, channeled whelks have an asymmetrical shell structure that prevents accurate or repeatable width measurements; therefore, we used LW as our primary width measurement because it is more precise than MSW (see Peemoeller and Stevens 2013) and is similar to the "width without spines" measurement SEX-SPECIFIC GROWTH OF CHANNELED WHELKS 463 used by Magalhaes (1948) to evaluate the size of knobbed whelks.…”

“…Therefore, any study on the growth of channeled whelks should be conducted on a sex-specific basis. Sex-based differentiation in growth may not occur among the smallest whelks; within the subsample we (Peemoeller and Stevens 2013) studied for maturity analysis, differential growth was not apparent until the whelks reached a size of about 80 mm SL (i.e., at 4 years of age). This statement is supported by the finding that the sex ratio (M:F) for whelks smaller than 110 mm SL was 1.26, compared with 4.3 for 110-160-mm SL whelks and 0.1 for whelks exceeding 170 mm SL (Peemoeller and Stevens 2013).…”

“…Whelks are typically slow growing and exhibit late maturity. There have been numerous studies on the biology of the knobbed whelk Busycon carica (Magalhaes 1948;Stevens 1976;Peterson 1982;Kent 1983;Edwards 1988;Walker 1988;Kraeuter et al 1989;Castagna and Kraeuter 1994;Power et al 2002Power et al , 2009Walker et al 2007;Avise et al 2010), but remarkably few studies have focused on the channeled whelk (Davis and Sisson 1988;Peemoeller and Stevens 2013). Most of these studies have addressed the biology, demographics, or reproduction of whelks, but few have studied long-term growth.…”

“…Results of both studies demonstrated that growth increased over time, declined with whelk size, and was highly episodic, with some individuals showing no growth for up to 2.5 years. We (Peemoeller and Stevens 2013) previously studied the reproductive biology, size, and age at maturity of channeled whelks in Buzzards Bay, Massachusetts, during 2010-2011 via dissection and histological examination of 473 individuals. Males had a maximum shell length (SL) of 175 mm, reached 50% sexual maturity (SM 50 ) at 115.5 mm SL or 6.9 years of age, and entered the fishery at 7.5 years of age.…”