Date of Award

Spring 2023

Project Type

Thesis

Program or Major

Biological Sciences

Degree Name

Master of Science

First Advisor

Elizabeth Fairchild

Second Advisor

Shelley Edmundson

Third Advisor

Winsor Watson

Abstract

The channeled whelk (Busycotypus canaliculatus) is a large predatory marine gastropod that supports an important commercial fishery along the eastern coast of the United States. Channeled whelk fisheries are state regulated, with each state enforcing slightly different regulations. In Massachusetts, the fishery is regulated by the Massachusetts’s Division of Marine Fisheries (MA DMF). Massachusetts’ channeled whelk landings peaked in 2012 at 3.6 million lbs., valued at $6.2 million. Since 2012, landings have decreased, 766,975 lbs. were landed in 2021 worth $3.1 million. Catch per unit effort (CPUE; lbs per trap haul) has also steadily decreased, indicating the resource is likely being overexploited. Therefore, one overall goal of the work presented in this thesis was to increase the sustainability of the channeled whelk fishery and provide a better understanding of whelk behavior that can help inform management decisions.Channeled whelks traps are baited with unique blends of ingredients. Typically, fishers use pieces of horseshoe crabs (Limulus polyphemus) as the main attractant. The use of horseshoe crab as bait is controversial because they play important ecological roles as both bioturbators and as a food source for migratory birds. Horseshoe crabs also are harvested for the biomedical industry which extracts Limulus Amebocyte Lysate (LAL) from horseshoe crab blood to test for pathogenic bacteria on medical devices. Therefore, the goal of the research presented in Chapter I was to create an alternative bait, that is both cost effective and does not rely on horseshoe crabs. In a laboratory experiment the traditional bait, horseshoe crab bait, was compared to a variety of alternative bait mixes, that included invasive species and/or fisheries processing wastes. Whelk attraction to bait was measured by using time-lapse video to quantify whelk interactions with baits during 24-48 hr trials. Baits containing a combination of green crab and clam products were interacted with by whelk between 24.2% less and 60.9% more than female horseshoe crab prosomas. These results indicate that an alternative bait is feasible and should be pursued further. At the least, these data indicate that male horseshoe crabs are as good as females, as bait, and their use might have less of an impact on the reproductive output of the populations. The elimination of horseshoe crab as bait, or simply the diversification in bait attractants and ingredients, will alleviate pressure on horseshoe crab fisheries. This would allow the continued bleeding of horseshoe crabs for LAL as well as help promote healthy horseshoe crab populations which can support shorebirds and diverse coastal marine ecosystems. Whelk attraction to bait was evaluated extensively in both the laboratory and the field to determine their efficacy compared to traditional baits. Using a whelk-trap video system (WTV), which is a traditional whelk trap fitted with a time-lapse camera in a waterproof housing, whelk interactions with alternative baits were observed. Traps (n=42) were deployed, and whelk activity was recorded with time-lapse video for a total of 1,778 hours throughout summer and fall 2022 with a mean soak time of 59.35 (± S.D. 32.65) hrs. Channeled whelk traps are a highly efficient method to catch whelks; as only one whelk out of 395 that entered the trap escaped. In field trap trials, channeled whelks demonstrated nocturnal feeding behavior with 90% of whelks entering the traps during nighttime hours (18:00-6:59 hours) when light intensity was  22 lumen/m2; the majority (65.4%) of whelks entered the trap within the first 12 hours regardless of bait tested. Traps with alternative baits caught 60% fewer whelk compared to traps baited with control female horseshoe crab parts, but bait type did not impact the size of whelk caught. Although not as attractive to whelks as horseshoe crab parts, the alternative baits were moderately effective and thus might have potential for diversifying baits in the fishery. Testing other fisheries processing waste streams and chemo attractants warrants future research to alleviate pressure on horseshoe crab populations. The final Chapter of this thesis focuses on whelk biological rhythms. In the laboratory, channeled whelk locomotion was recorded to determine if this activity was rhythmic. This was done by measuring whelk locomotion in flow-through tanks for 10 days while they were exposed to a diurnal photoperiod cycle, with the lights on from dawn to dusk in accordance with the season (approximately 13.25 hours light: 10.75 hours dark). Whelk locomotion was then measured for another 10 days in complete darkness to determine if whelk rhythms persist in constant conditions. Channeled whelk, much like other intertidal and subtidal marine invertebrates, exhibited a pattern of locomotion in alignment with the tides. The majority (72.7%, 8 out of 12) of whelks in this study expressed tidal rhythms but due to flow-through conditions and external cues it cannot be determined if this behavior is influenced by an endogenous clock. However, 90.9% (11 out of 12) of whelk in this experiment did not exhibit a daily rhythm of activity which was surprising given the nocturnal feeding behavior observed in Chapter II of this thesis. Having this baseline understanding of whelk activity rhythms can inform fishery management practices as rhythms impact when traps are most effective. This thesis provides baseline information on channeled whelk attraction to sustainable alternative baits compared to traditional baits. In addition, it builds upon previous knowledge of channeled whelk feeding behavior, locomotion, and trap dynamics. These results indicate that it should be possible to develop whelk baits that do not involve horseshoe crab parts, which would be useful to both the whelk fishery and horseshoe crab populations.

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