Over the last 30 or so years, the National Marine Fisheries Service (NMFS) has mandated a series of regulatory changes governing management of summer flounder, most which have been focused solely on managing quotas and overall catch of both recreational and commercial fishermen.
For the recreational community, the changes have been primarily in the form of reductions in possession limits and or increases in size limits intended to reduce overall harvest, in addition to seasonal closures. In reviewing NMFS’ own data, while it appears that ideology helped the fishery between 1988 and 2002, there’s strong evidence to suggest that same unwavering ideology has been the driving factor in a 30% decline in “spawning stock biomass” (SSB) from 2003 to 2015, the last year of reported statistics.
All data on the following charts that were used in developing this particular assessment was derived from Atlantic States Marine Fisheries Commission (ASMFC) report regarding Draft Addendum XXVlll presented to the public during the winter 2017 meetings.
From reviewing this data it is clear that the overall harvest between the years 1982 to 1988 appears to be the primary contributing factor leading to a precipitous decline in SSB experienced in the run up to a more restrictive management regime in the 1990's and beyond. SSB at the beginning of that period was ~26,000 metric tons declining to ~7,000 metric tons over the next seven years. Total catch during that time frame averaged ~20,000 metric tons or ~117% of SSB. In laymen’s terms, we were harvesting too high a percentage of the spawning stock and the root of the early problems in the fishery. The next graph illustrates exactly that point.
Over the next 14-year period 1989 to 2002, total catch was reduced through management measures to an average of ~11,500 metric tons per year or a ~43% reduction in catch from the period 1982 to 1988 when SSB plummeted. The decision at the time to reduce annual harvest made sense and the spawning stock and overall stock responded favorably to the session of overfishing.
At the time this was all occurring, there was a simultaneous shift taking place that should have registered cause for concern, but was either overlooked or ignored. While SSB was indeed building at a rate never before experienced historically, relative recruitment strength was declining at an alarming rate due to the disproportionate increase in harvest of larger female breeders. Recruitment strength is defined using NMFS’s own data as annual recruitment (fish at age 0) divided by SSB metric tons. In other words, it is a reflection of how many new fish are coming into the fishery based on every metric ton of the SSB and is therefore a measurement of the reproductive strength of SSB. The following charts illustrate that trend over the last 30-year period.
The above graph shows that the reproductive strength of the summer flounder SSB has been decimated over the last 20 or so years. The ratio peaked in 1993 at ~3,243 fish per metric ton of SSB and reached its low in 2015 of ~644 fish per metric ton. That constitutes an approximately 80% decrease in recruitment strength, the result of which has been a 13-year decline in overall SSB because as recruitment strength declines the number of fish maturing to create a sustainable SSB declines as well.
While this development was taking place, NMFS continued to manage the fishery focusing only on total catch. Size limits continued to increase while possession limits continued getting cut. In doing so, the unintended consequences of those decisions has been a significant shift in the gender composition of SSB giving rise to a precarious and sustained drop in recruitment strength over the last twenty years. This is because larger summer flounder (fish in excess of 18 inches) are overwhelmingly egg bearing females and under the upward shift of recreational minimum size limits they have become a disproportionately higher percentage of the recreational landings.
Additionally, larger summer flounder bring significantly higher market value for commercially harvested fish, resulting in added pressure on female breeders. But there's more to the picture - literally - when we look at the average recruitment as compared to the changes in recreational size limits!