Every year, the Chesapeake Bay Foundation (CBF) publishes an annual State of the Bay report, which grades the health of the bay on a variety of ecological factors while raising awareness of its most pressing issues. The recently released 2010 report, however, features a short section on Atlantic menhaden that includes vague and misleading language, which many scientists feel necessitates clarification. Menhaden management is the subject of this week’s (Jan 11-13,2011) meeting of the Atlantic States Marine Fisheries Commission’s (ASMFC) Atlantic menhaden technical committee.
WASHINGTON (Saving Seafood) — Jan. 10, 2011 — The larger a population, the better chance it stands to produce future generations, according to conventional wisdom. But that wisdom is inapplicable when it comes to the anomaly that is Atlantic menhaden, a small, oily fish more likely to be found in a medicine cabinet than on a menu.
Used to make fish oil and fishmeal, menhaden boast the evolutionary edge that enables females to produce enormous numbers of eggs. The success of those eggs, scientists say, is far more dependent on environmental conditions — weather, water quality and atmospheric pressure – than on anything else, including restrictions on commercial fishing
“Intuitively, it makes sense that less fishing means more menhaden,” says National Marine Fisheries Services biologist Joseph Smith. “But it doesn’t work that way. Based on years of data, there doesn’t seem to be a very good relationship between the number of spawners and the number of juveniles.”
Nonetheless, the CBF’s 2010 State of the Bay Report offers the conclusive and unsubstantiated claim that “the fishery must be managed conservatively so that large numbers are left in the water to benefit both the Bay and mankind.”
At issue here is how the ASMFC will conduct its stock assessment and determine appropriate approaches to manage the fishery. The CBF would like to see more conservative management, and, for the last several years, has been pushing the ASMFC to adopt a broader ecosystem approach.
Presenting a case for more conservative management, the CBF’s report states:
For many years, fisheries scientists, including those at CBF, increasingly have been concerned about declining numbers of menhaden and the impact the commercial fishery has on the menhaden population. Consequently, the [ASMFC] capped the Bay’s menhaden harvest at 109,020 tons in 2006 and extended the cap again in 2009, pending further study. A 2010 ASMFC analysis concluded that the population of Atlantic menhaden has fallen to historically low levels, having been overfished routinely for decades.
In fact, the 2010 assessment uses data only through 2008, with data from this last year showing that fishing mortality level barely above the overfishing limit. For menhaden, assessments consider two major factors: fishing mortality, which is the ratio of fish harvested to the total estimated population size; and biomass, which, in this case, is expressed as the number of mature eggs produced by the population. As reference points, fisheries assessments use targets (to represent the ideal level) and limits (to represent levels not to exceed). Scientist found the fishing mortality estimate for 2008 was barely over the limit (by 0.4 %), meaning that slight overfishing occurred in 2008. On the other hand, the biomass/egg reference point was right on target, suggesting that plenty of eggs were produced. Also, in the nine years prior (1999 – 2007), scientists concluded that overfishing did not occur at all. The CBF’s claim that menhaden have been “overfished routinely for decades” is a gross misstatement.
If there is justification to readdress management approaches to the fishery, it will not be based on the legitimacy of CBF claims. Its 2010 State of the Bay report includes other statements on menhaden that, although quoted in at least one news source, several fisheries experts repudiate on grounds that they are misleading or are simply too vague.
For instance, the report says that “Atlantic menhaden are among the most important creatures in the Chesapeake Bay,” and are “prodigious ‘filter feeders,’ swimming in large schools with mouths agape to consume plankton … thereby helping to maintain a balance of microscopic life in Bay waters.”
But Robert J. Latour, who head the ASMFC’s menhaden technical committee and conducts research at the Virginia Institute of Marine Science says, “recent scientific evaluations of the ecological role of menhaden have indicated that these fish may not be as important for improving water quality as originally thought, but a thorough assessment of their role has not be conducted and CBF did not comment on the level of importance. The report does state that menhaden help to ‘maintain a balance of microscopic life in Bay waters.’ This statement is not necessarily misleading, but it is somewhat uninformative since it is unclear what is meant by ‘balance’. Plankton communities are continuously in flux throughout Chesapeake Bay, and the mechanisms controlling the composition and abundance within these communities are complex and not well understood.”
The CBF’s report also mentions that “Menhaden are also essential prey for many important Chesapeake Bay species, including striped bass, bluefish, weakfish, ospreys, herons, and marine mammals.”
Indeed, menhaden, like numerous other prey species, are an important part of the food chain, but their presence in the diet of other species like striped bass is not as great as some believe. Conducted by the Virginia Institute of Marine Science, the Chesapeake multi-species monitoring and assessment program found that menhaden represented only about 8 percent of striped bass food in the Chesapeake Bay, with a variety of other species accounting up the balance.
Finally, concluding its rationale on the ecological importance of the fish, the report invokes author H. Bruce Franklin’s claim that menhaden are “the most important fish in the sea” – a curious assertion from an English professor with expertise in science fiction.
This week (Jan 11-13, 2001), the Atlantic menhaden technical committee of the Atlantic States Marine Fisheries Commission will meet to examine alternate approaches to setting reference points in preparation for the next fishery assessment, slated to begin in early 2012. Clearly, the CBF is of its own mind already. The section on menhaden in its 2010 State of the Bay report concludes that, “Further action by ASMFC to establish more sustainable harvest limits is expected. Because of menhaden’s critical ecological value up and down the food chain, CBF supports this likely action. The fishery must be managed conservatively so that large numbers are left in the water to benefit both the Bay and mankind.”
While CBF's conclusion sounds like common sense, it is not backed by the work and viewpoints of many leading scientists in the field.