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United States Department of Agriculture

Agricultural Research Service

Title: Delaware Bay Fish Health Monitoring: Evaluation of Copepod Parasitism in Atlantic Menhaden (Brevoortia Tyrannus)

Authors
item Pasnik, David
item Evans, Joyce
item Humphries, Edith - STATE OF DELAWARE
item Benz, George - TENNESSEE AQUARIUM
item Poynton, Sarah - JOHNS HOPKINS UNIV.
item Klesius, Phillip

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 25, 2004
Publication Date: April 25, 2004
Citation: PASNIK, D.J., EVANS, J.J., HUMPHRIES, E., BENZ, G., POYNTON, S.L., KLESIUS, P.H. DELAWARE BAY FISH HEALTH MONITORING: EVALUATION OF COPEPOD PARASITISM IN ATLANTIC MENHADEN (BREVOORTIA TYRANNUS). 60th ANNUAL NORTHEAST FISH & WILDLIFE CONFERENCE APRIL 25-28, 2004. MEETING ABSTRACT. 2004.

Technical Abstract: Juvenile Atlantic menhaden (Brevoortia tyrannus) were sampled from three Delaware bays in June-October 1999-2001 to assess menhaden health in Delaware waterways. Grossly visible Lernaeenicus radiatus were noted on 7.1% of the menhaden from all three sampling years, with evenly-distributed incidence from each bay. The highest incidence of parasitism was found in September of each year (15.5%), and 1999 exhibited the highest overall incidence (38.7%). A positive correlation between depth of capture, increasing fish size, and concurrent parasitism was found. However, the frequency of parasitism was not affected by changes in water temperature, dissolved oxygen, or salinity, nor by the presence of Pfiesteria-like-organisms or ulcerations on the fish. Histologically, the musculature at the site of copepod attachment showed a severe diffuse myositis often progressing to liquefactive necrosis. Gross examination of the copepods revealed fungal hyphae on the head of the parasites. These results indicate that Delaware Atlantic menhaden may be widely infested by copepods. However, the findings generate concern because of potential adverse effects by parasite attachment rather than as an indication of estuarine changes. Increased parasitism may facilitate pathogen entry into the fish, hinder osmoregulatory capabilities, and lead to ill-thrift, reducing the number of menhaden reaching reproductive age.

Last Modified: 11/26/2014
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