Friday, May 15, 2009

American Lobster Stock Assessment Yields Mixed Results

The 2009 peer-reviewed stock assessment report indicates the American lobster resource presents a mixed picture, with record high stock abundance and recruitment throughout most of the Gulf of Maine (GOM) and Georges Bank (GBK), continued low abundance and poor recruitment in Southern New England (SNE), and further declines in recruitment and abundance in NMFS Statistical Area 514 (Massachusetts Bay and Stellwagen Bank) since the last assessment. The Peer Review Panel noted particular concern regarding the status of the stock throughout the SNE assessment area and within Area 514 and recommended that further restrictions are warranted for both areas.

Despite current high levels of abundance and recruitment in GOM and GBK, the Panel recommended "that managers be particularly vigilant of recruitment patterns in these stocks and stand ready to impose substantial restrictions should recruitments decline." The Panel cautioned that productivity has been lower in the past. For example, landings in the GOM, which accounts for approximately 87 percent of the coastwide fishery since 2002, fluctuated without trend around 20 million pounds from 1930 - 1990. Those levels are substantially lower than current levels (average landings 72.8 million pounds between 2000-2007), possibly due to low recruitment and production. The current levels of fishing effort and harvest will not be sustainable if the stock returns to lower recruitment and production. This is of particular concern to the Panel since approximately 50 percent of available lobster are removed annually versus a removal rate of about 30 percent based on a biological reference point that would maintain 10 percent of the virgin spawning potential.

The Panel noted improvements to both commercial and fishery-independent data efforts. However, commercial data - both landings and particularly fishing effort - continue to be recorded piecemeal rather than universally. States should be strongly encouraged to standardize collection of fishery-dependent data and work toward mandatory universal coverage. The Panel also stressed "the need to continue this port and sea sampling so as to achieve representative coverage of all segments of the fishing fleet, because the length-based model depends of statistically representative length frequency data."

The 2009 stock assessment used a new length-based model developed by Dr. Yong Chen of the University of Maine. This model increased the ability to predict changes in population length structure and account for changes in management measures. The also model incorporated more fishery independent survey data.

Results showed current abundance of the GOM stock overall is at a record high when compared to the 26-year time series. Recent exploitation rates have been comparable to the past whereas recruitment has steadily increased since 1997. The exception is statistical Area 514 which has continued to experience very high exploitation rates and declines in recruitment and abundance since the last assessment. Continued restrictions are warranted given the persistence of low recruitment and its negative effect on total abundance and potential egg production. Across GOM, effort levels in recent years are the highest observed since 1982 (both in number of traps and soak time) and further increases in effort are not biologically advisable.

The new assessment showed current abundance of the GBK stock is at a record high compared to the 26-year time series and recent exploitation rates are at a record low. Recruitment has remained high in GBK since 1998. Sex ratio of the population in recent years is largely skewed toward females (approximately 80 percent from 2005 to 2007) for unknown reasons. The Technical Committee noted that the stock could experience recruitment problems in the future if females are sperm limited.

The new assessment showed current abundance of the SNE stock is the lowest observed since the 1980s and exploitation rates have declined since 2000. Recruitment has remained low in SNE since 1998. Given current low levels of spawning stock biomass and poor recruitment further restrictions are warranted.

The new assessment recommends revisions to the reference points set in the FMP. Revised reference points (see accompanying table) include median reference abundance and median effective exploitation rate thresholds for sexes combined from 1982-2003 in GOM and GBK and 1984-2003 in SNE. Stock status is determined by comparing stock-specific threshold values to the average reference abundance and effective exploitation rate for sexes combined during 2005-2007. An addendum is needed to implement these new reference points.

Based on the recommended reference points from the assessment, "overfishing" would occur if the average effective exploitation rate during 2005-2007 were higher than the stock-specific median threshold. A stock would be "depleted" if average reference abundance during 2005-2007 fell below the median threshold level. In either of these cases, corrective management action should be implemented. Given these recommended revised reference points, the GOM and GBK stocks are not depleted and overfishing is not occurring, while the SNE is depleted but not experiencing overfishing.

The Board accepted both the stock assessment and advisory reports and tasked the Technical Committee with providing recommendations for management and revising the reference points. Of particular concern is the status of the SNE stock. Copies of the stock assessment and peer review reports will be available by mid-May and can be accessed via the Commission's website at under Breaking News or by contacting the Commission at (202) 289-6400. For more information, please contact Toni Kerns, Senior Fishery Management Plan Coordinator for Management, at (202) 289-6400 or

No comments:

Post a Comment

Please leave your comments about saltwater issues.