Mark-Recapture
Research |
|
Understanding the population dynamics and movements of adult lobsters is critical for managing and sustaining the fishery. Although traps are the best way to catch lobsters with the least effort, it is hard to know exactly what the catch tells us about population size and change. And while divers can gather accurate counts of lobsters on the bottom, much of the lobster population extends well beyond the safe limits of diving. Tagging studies have long been a way to track lobster movements and growth, but what more can tagging studies tell us about lobster populations? The aim of this research is to take advantage of the accuracy of diver surveys to test how accurately mark-recapture studies with traps estimate lobster population size and survival. |
 Figure
1: Hauling lobster traps in the Gulf of Maine. |
Dr.
Wahle's team is using a dedicated set of research traps to catch (Fig.
1) and tag lobsters (Fig. 2) at regular intervals on specific
study areas
around Vinalhaven, Maine, U.S.A. |
 Figure
2: Bigelow scientists insert a numbered tag below the
carapace of a lobster
from Vinalhaven waters. |
Tag
returns (Fig. 3) from commercial harvesters are providing
important information
on the distance lobsters have moved from the original release
site. Using
recently developed methods that help us assess recaptures of
tagged lobsters,
we are able to estimate population size, gains, and
losses. |
 Figure
3: Map of lobster recaptures off of Vinalhaven. |
|
 Figure
4: Tagged sublegal adult lobster. |
Tags are flexible plastic streamers with two ends visible between the carapace and the tail. If you catch a tagged lobster, please report the following information to our research team, your buyer, call 800 339 9209 ext 125, or hail the R/V Alice-Siegmund on Channel 16. Date Caught |
|
|
|
To confirm the trap-based mark-recapture estimates of abundance, divers conduct an independent survey of the seabed. These diver-based counts verify the trap-based mark-recapture estimates of abundance (Fig. 5). This research is allowing us to translate trap catches into population size estimates and to go even a step further by providing a means to assess population turnover - a crucial component to managing the lobster fishery. |
| For more information on this project and to view an interactive map detailing lobster movements, visit the Island Institute's eAtlas. |
Figure
5: Results from the first year of the study indicate
mark-recapture-based
estimates are consistent with diver counts on the same
1-square-kilometer
area of seabed.