December 4, 2019 — SEAFOOD NEWS — A three-part study is underway to better understand life history, stock structure, and distribution of Atlantic halibut along the U.S. east coast. The study is being done by the Northeast Fisheries Science Center (NFSC) and The Cape Cod Fishermen’s Alliance with support from a Saltonstall-Kennedy grant developed by The Nature Conservancy.
Atlantic halibut was a reliable commercial fishery for nearly three centuries, but today is only commercially viable off the Canadian east coast. Commercial stocks in Canada appear to be increasing in recent years. The Canadian stock is fished on the southern Grand Banks and Scotian Shelf, extending to the northern edge of Georges Bank and in the Gulf of Maine. U.S. fishermen targeting other species are seeing more Atlantic halibut and wonder if stocks may be returning to U.S. waters as well.
Fishermen in Cape Cod and researchers at the NFSC want to know basic life history, stock structure, and where Atlantic halibut go during the year and during their lifetimes. The NFSC is helping with the life history component, especially reproductive biology.
That part of the study is focused on three questions: When and where do halibut spawn? Is there one overall population in the region, or are there several populations? And when do they mature?
“We would catch maybe 6 to 12 halibut a year in our scientific surveys during the last decade,” said Rich McBride, head of the NFSC’s Population Biology Branch. “That was not nearly enough for a study about the animal’s life history. We needed more samples than what we were catching.”
Two years ago the New England Fishery Management Council gave special permission for study participants to take up to six halibut per trip, exceeding the current trip limit of one.
The study needed 450 to 500 more samples from about 250 fish. Alliance members hit that target this year. They have provided about half the samples available for the study.
The Alliance, based in Chatham, Massachusetts worked with researchers to provide training to fishermen on collecting biological data. Fishermen learned how to gather samples from the heart, spleen, gonad (reproductive organ), earbones (for aging), and a fin clip. They recorded fishing location, the time, and the length and weight of the fish.
“When fishermen caught halibut in the course of a fishing trip, they would collect the samples,” explained George Maynard, research and policy coordinator for the Alliance. “Back on shore, I would collect the samples from the fishermen and bring them back to the lab for preservation and archiving. The tissue samples were all preserved and shipped to our collaborators in Canada for genetic analysis.”
Maynard prepared gonad samples and brought them to McBride at the NEFC for processing. McBride and his colleagues want to get an idea of each halibut’s maturity status.
“To get at those answers, we’re looking at developing eggs ‘under the hood,’ at the cellular level,” said McBride. “Having some sense of their current life history would be helpful as we move forward.”
“The next steps will be to combine these data with the length/weight and time of capture data from the fishermen, and aging data from the Massachusetts Division of Marine Fisheries,” said Maynard. “That will allow us to build a clearer picture of the size and age at which halibut reach maturity, and what time of year they spawn.”
The other two parts of the three-part study include a stock structure analysis using genetic samples led by the Bedford Institute of Oceanography in Halifax, Nova Scotia. The University of Massachusetts-Dartmouth’s School for Marine Science and Technology is leading a satellite-tagging effort to understand halibut habitat use and distribution.
This story was originally published on SeafoodNews.com, a subscription site. It is reprinted with permission.