Prevalence of a Trypanosome in Atlantic Cod (Gadus morhua) Especially in Relation to Stocks in the Newfoundland Area

Abstract

A study was initiated to ascertain the prevalence of a trypanosome in Atlantic cod (Gadus morhua) especially in relation to stocks in the Newfoundland area and as an aid in management and conservation. Highest prevalences were recorded in fish taken off the Labrador coast (ICNAF divisions 2J and 3K, 94 and 90%, respectively). Trypanosomes were not as prevalent in fish collected from the northern Grand Bank (46%, division 3L) or from the southern Grand Bank (13 and 16%, divisions 3N and 3O, respectively). A further decrease in prevalence occurred among fish collected on the Flemish Cap (10%,, division 3M) and St. Pierre Bank (8%, subdivision 3Ps), while the lowest levels (4%) were apparent in cod taken from the Gulf of St. Lawrence (divisions 4R and 4S). Fish sampled at inshore localities reflected prevalences corresponding to some extent to offshore localities. Cod taken on coastal Labrador and from northern Newfoundland have a high prevalence of trypanosome infections while in the more easterly bays, intermediate levels occur. A conspicuous decrease in prevalence was apparent in a sample taken from the most easterly inshore locality (Portugal Cove) and from two others on the south coast of Newfoundland. Lowest prevalences were noted among fish taken at four inshore localities in the Gulf of St. Lawrence. These results, based on prevalences of infection, support conclusions from other studies that there are at least six stocks of cod in the Newfoundland area with some degree of mixing.Key words: trypanosome, prevalence, cod stocks, Newfoundland–Labrador, ICNAF