Date of Award

Spring 2018

Project Type

Thesis

Program or Major

Zoology

Degree Name

Master of Science

First Advisor

Winsor H Watson III

Second Advisor

Jason S. Goldstein

Abstract

The overall goal of this research was to explore the factors that influence the distribution of egg-bearing (berried, ovigerous, eggers) lobsters along the coast of New Hampshire (NH), specifically near the Isles of Shoals (IOS). Initially, I determined the distribution of egg-bearing lobsters based on catch rates (#/trap haul) from New Hampshire Fish and Game Department’s (NHF&G) Lobster Sea Sampling Program. Based on these data there appeared to be a higher abundance of these lobsters on the eastern side of the IOS, which is closer to areas that are deeper and characterized by higher current flow. To confirm this finding I designed a trap-based study to assess lobster population demographics on both sides of the IOS (east vs. west) (Chapter 1). Trawls (traps tied to a common line) were set on similar substrates, depths, and comparable soak times on both the east and west side of the IOS so non-biased comparisons could be made between the two areas. Results suggest that traps fished on the eastern side of the IOS caught a significantly higher number of egg-bearing lobsters than those set on the western side. There was also a higher abundance of eggers with pre-hatch eggs in shallow water, and more females in the process of hatching eggs in deep water. A similar pattern was also apparent in two other surveys conducted along the coast of NH; the Lobster Sea Sampling Program and the Coastwide Ventless Trap Survey. These data, taken together, led to my hypothesis that egg-bearing lobsters move from shallow to deep water just prior to the time when their eggs are due to hatch.

In the summers of 2016 and 2017 I tested this hypothesis by tracking the movements of 12 late-stage egg-bearing lobsters using acoustic telemetry (Chapter 2). I acquired acoustic tags for these animals (VEMCO V13AP) that transmitted depth (m) and activity (m/s-2) every ~ 90 seconds and logged these data using an array of fixed VR2W receivers in the same area where the trap survey was conducted. All but one (92%) of these lobsters moved to deep water prior to the time when we predicted their eggs would hatch, based on using the Perkins Eye Index assay from samples removed from pre-tagged animals just before they were released. A total of 3 lobsters (25%) hatched eggs in deep water (30-40 m) within the array, while 67% left the array generally in a south, southwesterly, direction towards deeper waters. These results supported my hypothesis and indicated that the behavior of berried females appears to shift just prior to the time when their eggs are predicted to hatch. At the end of both Chapters of this thesis I speculate on the advantages of this behavior and the factors that might guide the movements of these lobsters.

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