Biological oceanographer William K. Macy at the University of Rhode Island’s Graduate School of Oceanography (GSO) has examined the population structure of the long-finned squid (Loligo pealeii) during the winter offshore season and the seasonal trends in its age structure both inshore and offshore.
One of the purposes of the study was to assess whether an increase in the winter offshore fishery is causing the recent decline in the squid population inshore and, thus, a decrease in landings. Also taking part in the study was Jon K.T. Brodziak of the Northeast Fisheries Science Center in Woods Hole, Massachusetts.
In the study, reported in the ICES Journal of Marine Science, Macy collected a number of samples from both the inshore and offshore fisheries of this species of squid to determine their age when caught.
He found that the inshore fishery harvested squid hatched during winter, while the offshore fishery harvested squid hatched during summer and early autumn. Although squid harvested in the inshore fishery tended to be larger than those harvested offshore, the median age of maturity from both fisheries was about 150 days.
Macy’s study found that the sampled squid were all approximately the same age, regardless of time of year and location. With two main spawning periods, each of the two fishing seasons catches squid at the same stage of life and at the same ranges of age. The squid caught by the offshore fishery were spawned during the previous inshore season and squid caught by the inshore fishery were spawned during the winter.
This five-month time period, plus the several weeks required for hatching and post-spawning mortality, supports the scientists’ view that the squid’s typical lifespan is approximately six months.
Thus, the interaction between inshore and offshore fisheries has important implications for fishery management because it suggests that conservation efforts to maintain the spawning cycle need to be jointly pursued for both fisheries. In fact, the data strongly suggest that the inshore fishery is entirely dependent upon squid which survive the winter offshore fishery season.
“Because of the short typical lifespan, quarterly fishery catch quotas have been introduced to insure that sufficient squid survive to reproduce during the following seasons,” said Macy. “It is thus hoped that consistent sustainable yields of this valuable resource can be maintained. Common squid landings by Rhode Island and the nearby states of Massachusetts, New York, and New Jersey accounted for 99% of the value of the entire Atlantic coast catch of $23 million (ex-vessel) for the year 2000. Rhode Island landings alone (close to $11 million) amounted to almost half of the total. Within Rhode Island, squid landings ranked second to lobsters in value.”
Macy, a resident of Wickford, is an assistant marine research scientist at the URI Graduate School of Oceanography. He received a B.A. from Middlebury College in Vermont, and his M.S. and Ph.D. in oceanography from the University of Rhode Island.
Journal
ICES Journal of Marine Science