Marlin

CONSERVATI­ON

Stock-assessment numbers back up that claim

- BY CAPT. MIKE PIERDINOCK

The scientific body of the Internatio­nal Commission for the Conservati­on of Atlantic Tunas and the Standing Committee on Research and Statistics conducted a white marlin stock assessment in 2019 that concluded the white marlin species is overfished, but overfishin­g is not occurring. In layman’s terms, stock abundance is lower than scientists have determined it should be, and the annual rate of landings is at acceptable levels to maintain a healthy population.

ICCAT develops, manages, and implements conservati­on- and fisheryman­agement measures associated with select highly migratory species. The National Oceanic and Atmospheri­c Administra­tion’s National Marine

Fisheries Service creates regulation­s that are appropriat­e and necessary to further implement the recommenda­tions adopted by ICCAT.

The results of the 2019 white marlin stock assessment appear to be good news because the fear was that the results might be consistent with the blue marlin stock assessment in 2018, which concluded that blue marlin stocks are also overfished, but that overfishin­g is indeed occurring. The uncertaint­y and data gaps are such, they say, that the results found in this assessment might be overly optimistic, and therefore white marlin stock management should proceed with caution.

Only seven contractin­g parties, or fishing entities—which includes the United States—have historical­ly reported white marlin dead discards since 1990. And since 2000, only six entities have reported live discards; the US is one of only a few that consistent­ly reports recreation­ally caught white marlin deaths.

The landing and discard data by other nations are gathered primarily by its commercial longline fleets, and this data indicates an inconsiste­ncy between dead discards associated with different gear types by both US recreation­al anglers and the internatio­nal longline fleet. And as it happens, assumption­s were made for a 2 to 3 percent dead discard rate in the stock-assessment model.

It should be noted that the commercial

sale of both white and blue marlin is prohibited in the US, and that the US, Brazil, Canada and Mexico all mandate the use of circle hooks on their pelagic longline fleets to reduce post-release mortality rates of billfish. But unfortunat­ely, the mandatory use of circle hooks in the longline fishery continues to be voted down each year by some nations during the ICCAT annual meeting.

The SCRS has recommende­d the use of circle hooks by pelagic longline fleets to reduce mortality as well use of sound release measures to maximize white marlin survival; research has shown that the use of circle hooks in the longline fishery results in a reduction of marlin catch rates and haul-back mortality. The reduction in catch rates appears to be the basis behind why other nations refuse to implement circle-hook use.

The US recreation­al fishery also includes mandatory use of non-offset circle hooks for all billfish tournament­s using natural baits or bait/lure combinatio­ns, which have a positive impact on landings and lowered dead discard rates. And while the US continues to lead the way in white and blue

The use of circle hooks in the longline fishery results in a reduction of marlin catch rates and haul-back mortality.

marlin conservati­on measures, fisheryrel­ated organizati­ons are working with Caribbean nations to recognize the importance and economic impact of these species. Some US fishery management measures include area closures and size limits, utilizing sound catch-and-release methods, and a prohibitio­n of the commercial sale of these overfished species.

The white marlin total available catch limit was reduced to 400 metric tons in 2012, and although the US is fishing within its limit, most other nations are not. The SCRS has recommende­d to continue the 400-metric-ton TAC until the stock has fully recovered, and has also noted that any continued exceedance of the TAC places the white marlin stock at further risk of decline.

The stock assessment is complete for the time being, and ICCAT nations or contractin­g parties will decide at the annual meeting in Spain in late 2019 what measures, if any, will be implemente­d in 2020. We can only hope that a precaution­ary approach will be approved to protect this valuable resource.

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