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Has the status of fish stocks changed?

Indicators: Biomass | Fishing Mortality

Key Findings

  • Average biomass (B/BMSY) decreased 20.4 percent during the baseline period, with an eventual slight 1.2 percent increase following implementation of the Northeast Multispecies Sector Program.
  • The proportion of stocks with depleted biomass (B<0.5BMSY) has increased from 27 percent to 53 percent of assessed stocks since the start of the extended baseline period.
  • Biomass changes have been variable across stocks since the catch share program began, with some stocks experiencing an increase, some a decrease, and some largely staying unchanged.
  • Several stocks were overfished during the catch share period, requiring rebuilding plans and reductions in catch limits.

Interactive Chart Story

Metrics

This indicator shows the abundance of fish stocks in the fishery management area.

Analysis

Baseline: Before Catch Share Program

Along with the project baseline beginning in 2002, an extended baseline beginning in 1980 illustrates long-term trends in stock status. The average biomass ratio declined by 54 percent from 1980 to 1985. By the early 1990s, the biomasses of many groundfish stocks reached record, or near-record, lows. For example, the total cod biomass on the Scotian Shelf and in the Gulf of Maine was estimated to be a small fraction of what it was during the nineteenth century (History of Fishery).

The average biomass ratio of groundfish stocks ranged between 33 and 50 percent of the levels that would provide the highest long-term average catches, or maximum sustainable yield (MSY). In three stocks—Gulf of Maine (GOM) haddock, Georges Bank (GB) haddock, and Atlantic pollock—biomass ratios exceeded BMSY for most of the project baseline. In contrast, seven groundfish stocks (GB cod, Eastern GB cod, GOM cod, white hake, SNE/MA winter flounder, CC/GOM yellowtail flounder, and GB yellowtail flounder) were overfished for all eight years of the project baseline. Four additional groundfish stocks (witch flounder, American plaice, SNE/MA yellowtail flounder, and Acadian redfish) were overfished in at least two years of the baseline period. Biomass ratios of individual stocks were variable over the extended baseline, with some stocks showing an increasing trend and others showing a declining trend.

The proportion of stocks that were overfished during the project baseline did not demonstrate notable increasing or decreasing trends. The majority of stocks had low biomass levels, but between two and five stocks each year had biomass levels that exceeded MSY. Four stocks—Acadian redfish, Atlantic pollock, SNE/MA yellowtail flounder, and GB haddock—showed improvement in status, increasing from biomass levels below BMSY to above the biomass reference point. American plaice recovered from overfished status, while status of GOM haddock and witch flounder declined during the project baseline. Both GB and GOM cod stocks showed slight improvement in biomass beginning in 2006, but remained well below MSY levels .

During Catch Share Program

Although the average biomass ratio of allocated stocks increased from 2010 to 2015 by 21 percent, the proportion of stocks overfished (B<0.5BMSY) remained just above 45 percent in the first six years of the Northeast Multispecies Sector Program, and increased by 12.7 percent three years into the program. Thus, the aggregate picture of stock status belies considerable differences in individual stock status. Both GB and GOM cod stocks remained below overfished levels, as has SNE/MA yellowtail flounder. In contrast, other stocks have recovered from historical overfishing, and other stocks have reached very abundances. Most prominently, haddock stocks are all well above BMSY. In general, few stocks exhibited either a strong positive or negative change in status during the first six years of the catch share program. This lack of dramatic change matches expectations; we would not expect biomass of stocks to be impacted because of the implementation of the catch share program or the implementation of annual catch limits (ACLs). Rather, it may take one or more fish generations (at least 5 years) to see improvements in biomass levels. However, the continued low biomass levels of some stocks likely have implications in setting ACLs and constraining catch of healthy populations (Financial Viability of the Fishery: Landings). Thus the continued occurrence of overfished stocks through the catch share period.

Data Gaps and Limitations

Data for this indicator came from the most recent fisheries stock assessments reviewed in 2015 for 16 of the 18 stocks allocated in the Northeast Multispecies Sector Program. The 2015 GOM winter flounder assessment was not deemed to be sufficiently accurate for giving management advice. The northern and southern windowpane flounder assessments did not use age- or size-structured population dynamic models, but instead tracked survey- based abundance indices. The GB yellowtail flounder assessment also did not use a population model so was excluded from this analysis. The eastern GB haddock assessment did not estimate biomass reference points. Given that assessments are conducted on a varied schedule for individual stocks, data for recent years are typically not uniformly available. Therefore the analysis uses the dataset available on an individual stock basis, and in the cases where years have not been assessed, stock biomass from the most recently assessed year is used.

It is important to remember that responses in stock biomass to changes in management or other factors take considerable time to realize. The response time varies from species to species based on generation time. Furthermore, the response may be partially or entirely masked by other factors, such as environmental conditions and predation. It may take a number of years of data to properly identify relevant trends.

Information Sources

Northeast Fisheries Science Center (2012). Assessment or Data Updates of 13 Northeast Groundfish Stocks through 2010. US Dept Commerce, Northeast Fish Sci Cent Ref Doc. 12-06; 789 p.

Northeast Fisheries Science Center (2015). Operational Assessment of 20 Northeast Groundfish Stocks, Updated Through 2014. US Dept Commerce, Northeast Fish Sci Cent Ref Doc. 15-24; 251 p.

Stone, HH, EN Brooks, D Busawon, Y Wang (2015). Assessment of Haddock on Eastern Georges Bank for 2015. Transboundary Resources Assessment Committee.

Wang, Y, L O’Brien, I. Andrushcheknko, KJ Clark (2015). Assessment of Eastern Georges Bank Atlantic Cod for 2015. Transboundary Resources Assessment Committee.

Updated: May 2018

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