Striped Mullet Stock Assessment Underway
Charlotte County Sea Grant Extension
This article appeared in the May 2011 edition of Water LIFE magazine
The Florida Fish and Wildlife Conservation Commission – Fish and Wildlife Research Institute (FWC-FWRI) began a one year targeted sampling effort to assess the stock of striped mullet in Charlotte Harbor and Tampa Bay in February of this year. The last stock assessment for this species took place in 2005.
Striped mullet are distributed worldwide in most coastal waters and estuaries of tropical and subtropical seas. They were actually one of the first fish I saw two months ago while snorkeling in Hawaii. Tagging data show that some striped mullet move between Florida’s Atlantic and Gulf coasts. Striped mullet reside in bays and tributaries but spawn offshore in depths up to 5,400 feet during November through early January. Striped mullet grow to about 6-7 inches fork length in one year and can reach 9–13 years of age. Females mature at 2–3 years old when about 11.5 inches. Florida mullet are considered vegetarians although they are known to eat cocopods and other small organisms. They are also the only fish to have a gizzard, much like a chicken, which is used to grind up and digest plant material.
FWC-FWRI monitors fish populations throughout the year. The Charlotte Harbor Field Lab has boats out most days pulling nets for this purpose. As part of their ongoing sampling, they use 70 foot seines to assess juvenile stocks and 600 foot seines to assess adult populations. The 600 foot seine does not work well for assessing mullet however. This is because mullet jump and can easily jump over the net. So, for the mullet stock assessment a trammel net is used.
In the Charlotte Harbor sampling effort, the harbor is divided into four sampling regions. Each month a crew goes out in search of at least 80 mullet in each of the four regions. Thirty mullet (from at least two different locations within each region are collected and brought back to the lab. Another 50 are measured and released. Any additional mullet caught are also measured and released. Back at the lab, the 30 mullet are measured, weighed, sex is determined and ear stones are removed to age the fish. This information along with the ear stones are sent to St. Petersburg for further analysis.
I went out with the Charlotte Harbor group in March to sample for striped mullet in the Gasparilla Sound region. The process involved driving around looking for mullet jumping and then setting the trammel net. Spring and Summer time sampling is not very easy because the mullet don’t school up like they do in the Fall and Winter when they are heading offshore to spawn. A number of times we saw mullet jumping only to find out the five jumps we saw were from the five mullet located in that area. Other times our catch was mixed with silver mullet, a non target species. This stock assessment is only looking at striped mullet. Striped mullet has more commercial value as both a food fish and for its roe, particularly in the Asian market. Silver mullet (also called white mullet) also has commercial value but primarily as bait for sport fishing.
Sampling for the striped mullet stock assessment will continue until February 2012 with the stock assessment results following.
Highlights from the 2005 striped mullet assessment:
- The commercial fishery constituted 84% percent of the total landings during 2000-2004. The west coast of Florida contributed to 85% of the total commercial landings during 2000-2004.
- Since the 1995 net-ban, Florida’s commercial landings have sharply declined to an annual average of 8.1 million pounds, a 67% reduction if compared to the recent historical (1967-1990) average level of 25 million pounds. The total commercial landings in 2004 were 7.6 million pounds. The number of commercial fishing trips declined from an annual average of 62,345 trips before the net-ban took effect (1986-1994) to 28,785 trips after the net-ban took effect (1995-2004), a total reduction of 54%.
- The proportion of the roe-season landings to the total landings increased during the post net-ban period in the southwest region and remained unchanged in the east coast and northwest regions.
- Statewide recreational landings of striped mullet have been variable from 1.0 million pounds in 1985 to 5.1 million pounds in 1996. Recreational landings have averaged 1.6 million pounds during 2000-2004.
- Commercial catch rates for striped mullet increased following the elimination of entangling gears in Florida waters on both coasts. This increase probably reflects the increase in the stock size.
- Current stocks in the east coast, NW, and SW regions appear to be healthy and current levels of fishing effort appear to be sustainable.
Source: The 2005 update of the stock assessment for striped mullet, Mugil cephalus, in Florida. Behzad Mahmoudi, Florida Fish and Wildlife Conservation Commission.
Betty Staugler is the Florida Sea Grant Agent for Charlotte County. She can be reached at 941.764.4346
Sea Grant is part of of the University of Florida IFAS Extension