2014 menhaden assessment optimistic for stock

First published in Landings, April, 2015.

Lobstering requires a strong back, a sturdy boat and a whole lot of bait. If you don’t have good bait and enough of it, you are not going to catch many lobsters.

So when the Atlantic States Marine Fisheries Commission (ASMFC) in 2012 cut the allocation of menhaden that could be caught, it affected Maine’s lobstermen. Menhaden, also known as pogies, are the second-most used bait among the state’s lobstermen, according to data compiled by the Maine DMR. The migratory fish can be found along the Eastern seaboard, from northern Florida to the Gulf of Maine. The reduction fishery harvests the fish for their oil; the bait fishery catches menhaden for lobster bait.

The majority of harvested menhaden are processed for their oil. The remainder are used for lobster bait. Photo courtesy of the Bay Journal.

The majority of harvested menhaden are processed for their oil. The remainder are used for lobster bait. Photo courtesy of the Bay Journal.

The ASMFC 2012 benchmark assessment was an update of the official assessment produced in 2010 which had concluded that menhaden populations were experiencing overfishing. To ensure the sustainability of the fish, which is an important food for a multitude of marine species, particularly striped bass, the ASMFC reduced the total allowable catch of menhaden to 170,800 metric tons, a 20% reduction from landings in 2011. That quota was allocated among different states based on each state’s landing history for 2009-2011. When the quota in a particular state was met, the fishery in that state had to close.

“One of the issues was the model [used in the assessment process] had a retrospective pattern,” explained Michael Waine, fisheries management plan coordinator for ASMFC. “That means when you add in a new year of data the results of the previous years assessment change. Overall, the model was having a hard time fitting the data so it was giving inconsistent results.”

Those who processed the fish for its oil, specifically companies such as Omega Protein, based in Virginia, argued that the 2012 stock assessment was flawed. “Similar issues existed in the last peer reviewed assessment [2010 assessment], but ultimately that assessment passed review and was acceptable for management use,” Waine added. “In 2012, when the technical committee updated the assessment the problems had gotten worse, so even though updated assessments are not peer reviewed the technical committee still stepped back and wanted to dig deeper to fix the issues.”

ASMFC manages menhaden on the basis of the stock’s biomass and fecundity. That means it looks at how many fish are out there and how many eggs are produced by those fish. Older fish are assumed to produce more eggs. The goal of menhaden management is to have enough eggs available in the ocean each year to take advantage of favorable environmental conditions, thus fecundity is judged one of the most reliable measures of sustainability.

To improve its assessment model, the ASMFC’s menhaden technical committee first created two new regional adult abundance indices, generated using nine fishery-independent survey data sources. In addition, the assessment broke the overall fishery into component parts based on geographic location and the use of the fish. It divided the menhaden fishery into the northern bait and reduction fisheries and the southern bait and reduction fisheries, then took a look at the age of the fish caught in each fishery.

“For two years we went through every data set that had menhaden in it. We looked again at one reduction fishery data set going back to the 1950s that we had previously examined for length [data] and found that it had maturity data as well,” Waine explained.

menhadenLandings data used in the assessment indicated that older menhaden are much more likely to be found in the northern range of the fishery, with fish caught in New Jersey and northward being primarily three to four years in age. The assessment model recognized that a higher proportion of older fish, greater than four years in age, survive and produce an abundance of eggs.

The assessment also examined menhaden mortality rates, i.e. the number of fish that were being removed from the stock due to fishing or natural death. It found that menhaden are experiencing some of the lowest levels of fishing mortality recorded since 1955. The stock is projected to be at about 170% of its target abundance level measured in terms of annual egg production. The menhaden population is near record levels and is currently well above historic averages.

“This is exactly how science works, as a progressive exercise,” Waine said, referring to the previous two years of work on the assessment model. “We saw there was a problem and that the problem was getting worse so the technical committee reevaluated the mechanisms involved. The committee wanted to ensure that the resource was being managed with the best available science.”