Striped Bass Health and Forage Base Investigation
The high percentage of striped bass in the Chesapeake Bay in poor nutritional condition raises concern about the declining forage base for all predator species that utilize the Chesapeake Bay, including the common loon. During 1997 and 1998 over 60% of the striped bass from Maryland’s portion of the Chesapeake Bay that were examined by the Chesapeake Bay Ecological Foundation had little, or no fat in the body cavity and exhibited signs of poor nutrition and starvation; approximately 12% of these fish had visual external lesions, ulcers, or sores. Ulcerative Dermatitis in Chesapeake Bay striped bass was first reported to the Maryland Department of Natural Resources in September 1994, following poor recruitment for the 1993 year class of Atlantic menhaden in the Chesapeake Bay. During the fall and winter season the water temperatures decrease and forage becomes more available. At this time, the condition of the striped bass population improves, with most of the lesions and sores healing, indicating that the chronic outbreak of various skin anomalies may be related to poor nutrition coupled with peak water temperature in late summer. The CBEF is currently working with officials from the University of Maryland Eastern Shore, Chesapeake Bay Program, MD-DNR, U.S. Fish and Wildlife Service and the National Marine Fisheries Service to investigate what effect reduced numbers of Atlantic menhaden have on the diet and health of fish and bird populations in the Chesapeake Bay and along the Atlantic coast.
No other fish has the capability to replace this unique species. Historically, during their residence in the bay, a healthy population of Atlantic menhaden had the capacity, in less than two days, to filter a volume of water equal to the entire Chesapeake Bay. The Atlantic menhaden stock was considered severely depressed from 1964 through 1968 when the population was 4.65 billion fish, according to the Atlantic Menhaden Fisheries Management Plan. The estimated population of 4.55 billion fish in 1997 is lower than the 5 year average for the mid sixties. Even though the total coastal Atlantic menhaden population has declined 58% since 1991, landings in the bay have remained relatively high. Landings averaged 150,000 metric tons per year and actually increased to approximately 160,000 metric tons in 1997. During the 1997 season, approximately 60% of the total weight of Atlantic menhaden caught on the entire east coast of the United States were harvested from Virginia’s portion of the Chesapeake Bay. Poor recruitment of Atlantic menhaden in recent years, coupled with the concentrated effort of the reduction fishery in Virginia’s portion of the Chesapeake Bay and adjacent coastal waters, has substantially reduced the Atlantic menhaden population in Maryland’s section of the Chesapeake Bay. The 1998 MD-DNR Juvenile Finfish Seining Survey index for Atlantic menhaden is the lowest since 1970, indicating another year of poor recruitment for juvenile menhaden in the Chesapeake Bay and the Atlantic Coast based on data examined in our investigation that correlated Maryland’s seining survey results with the NMFS’s population estimates for Atlantic coast menhaden recruitment.
A MD-DNR report from the 1960’s stated, “Previous food habitat studies by us have indicated that during the summer and fall months, most striped bass of legal size (12” minimum) or larger have switched from a diet of predominantly anchovies to a diet of menhaden”. Research conducted by Hartman and Brandt on the diet and growth of striped bass, printed in Transactions of the American Fisheries Society 124:520-537, 1995, stated: “Atlantic menhaden represent the largest percentage of the diet of age-2 and older striped bass. Atlantic menhaden are of considerable importance to annual production of striped bass and bluefish, because much of the annual growth of these predators occurs when menhaden dominates the diet”. Recent striped bass diet studies in the Chesapeake Bay indicate an increase in the consumption of bay anchovy by age-2 and older striped bass since Atlantic menhaden have not been available in sufficient numbers to provide an adequate source of forage, however, bay anchovy numbers have now been reduced to historically low levels as well, resulting in a decrease in growth rates for striped bass because of their strong dependency on these two species. The MD-DNR Juvenile Finfish Seining Survey data indicates the bay anchovy population declined dramatically, following low recruitment of Atlantic menhaden in 1993. Striped bass 18” in total length, examined in a 1998 CBEF survey, averaged 23% less in weight, compared to healthy striped bass tagged and released in a CBEF and MD-DNR study in 1984, when Atlantic menhaden were more abundant in Maryland’s portion of the Chesapeake Bay. The 1996 – 1997 USFWS Federal Aid Report F-42-R-10, prepared by the MD-DNR stated, “since 1994 age-5 and age-6 striped bass harvested in the gill net fishery have decreased in weight and in length. The mean weight of 6 year old striped bass in 1997 equaled the mean weight of 5 year old fish in 1994 and the mean weight of 5 year olds in 1997 equaled that of 4 year olds in 1994”. In a survey conducted by the CBEF in 1997 and 1998, in Maryland’s portion of the Chesapeake Bay, Atlantic menhaden were found in 6% of 203 striped bass examined, and in a study conducted by the University of Maryland for the MD-DNR, from April 1998 to October 1998, Atlantic menhaden represented only 1% of the food items identified in 482 striped bass. According to population estimates from the ASMFC’s management plan for Atlantic menhaden and striped bass in 1982, there were approximately 1500 age-0-2 Atlantic menhaden for every kilogram (2.2 lbs.) of striped bass age-2+ in the Atlantic coastal population, and by 1996 the ratio had decreased 96%, to approximately 60 menhaden per kilogram of striped bass age-2+ in the coastal population.
On June 8, 1998, at the request of the MD-DNR, the CBEF presented data from it’s investigation into the current status of the Atlantic menhaden stock to the Atlantic Menhaden Management Board for their annual review. The ASMFC announced their decision on June 11, 1998 to conduct an external peer review of the current stock assessment for Atlantic menhaden. The CBEF submitted the results of their investigation and gave testimony during the Peer Review Meeting held November 16-18, 1998, in Baltimore MD. On November 21, 1998 the CBEF, Coastal Conservation Association of Maryland, and the Chesapeake Bay Foundation sponsored a symposium, “Striped Bass In Crisis?”, at the Kent Island High School Auditorium, with approximately 200 concerned citizens in attendance.