Date of Award
Master of Science in Animal Science
The three year study consisted of two phases. Phase one investigations included movement, growth, age and size determinations, and population structure of areas of Narragansett Bay, Rhode Island. Aspects of the commercial fishery which appeared lacking in data necessary to optimize results from fishing effort were investigated in phase two. Included were market size determination, bait containers, trap designs, and seasonal catch variation by fishermen.
Movement of marked channeled whelks along the bottom of the bay was random and not correlated with other variables such as growth or month of the year. Growth of all returned tagged animals averaged 2.6 millimeters regardless of time from release to recapture.
Tag returns indicate that growth layers on the shell surface are a useful method of identifying population segments. An estimation of age may be derived from the formula: estimated age = 0.76 (width in nun) + 0.07 (weight in gm) - 35.65 (accuracy ± one growth layer), which was constructed with data collected in this investigation. Based on width data, the population size distribution of the study area may be considered homogeneous.
All areas sampled show no single population segment, with the dominant constituent having four to five growth layers and a width of 141-210 mm which make the animals large enough to yield sufficient meat to warrant processing commercially.
Fresh horseshoe crab was found to be the superior bait tested. Frozen horseshoe crab, and a frozen mixture of horseshoe crab and scrap fish, were found to be less effective baits which did not show a seasonal chance in effectiveness of catch.
Several bait containers were tested. It was found that a plastic mesh onion bag vas a suitable container for frozen baits.
It was determined that the use of plastic coated wire in trap construction was only useful in combination with wood, and thus no method of completely eliminating shipworm damage was devised.
Laboratory studies reveal that whelks escape from unbaited traps at the same rate per day over a period of time, and that the use of a retarding lath in traps is sufficient to retain these animals.
The minimum weight necessary for efficient processing is 164 grams. Most animals of this weight had 4-5 shell growth layers. Smaller animals yield less meat (weight) in proportion to shell weight, and the yield per fifty pound bushel is less.
Analysis of variance for catch data from daily trap hauls, weekly replicates, and monthly replicates reveal that the error term is so large, that it effectively masks any treatment effects from months or weeks so that when a type I error ≤5.0% is accepted, no significant differences exist between monthly or weekly catch. Accepting a type I error ≤25% there is a significant difference between months.
Sisson, Richard T., "Biological and Commercial Fisheries Related Research on the Channeled Whelk Busycon canalculatum (Linne) in Narragansett Bay, Rhode Island" (1972). Open Access Master's Theses. Paper 2403.