Premium
Aspects of the biology of Sprattus sprattm (L.) in the Medway Estuary
Author(s) -
Broek W. L. F.
Publication year - 1979
Publication title -
journal of fish biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.672
H-Index - 115
eISSN - 1095-8649
pISSN - 0022-1112
DOI - 10.1111/j.1095-8649.1979.tb03627.x
Subject(s) - sprat , biology , estuary , copepod , population , fish <actinopterygii> , zoology , fishery , ecology , herring , crustacean , sociology , demography
Fish samples were taken monthly over an eight‐hour day period between 1973 and 1975. In addition, separate night samples were collected during 1974–75. The present study considers the sprat component of the catch and examines aspects of the fish's biology and its accumulation of chlorinated hydrocarbon compounds and heavy metals. Sprats were present on every sampling date and, generally, totals were highest during late autumn/early winter. They formed 61.1 % of the catch by numbers and 17.5% by weight. Night samples contained an unexpectedly large number of sprats and with mean lengths significantly greater than those in day samples. Changes in monthly length‐frequency distributions suggested double spawning during 1974, perhaps the result of a mild winter. Sprats were infected with two copepod ectoparasites; Lernaeenicus sprattae (Sowerby) and L. encrasicola (Turton). In each case infection was low, affecting only 6.6 and 0.9% of the population respectively. Levels of chlorinated hydrocarbons and heavy metals were also low in whole sprat tissue. Values of DDDT, dieldrin and PCBs were at a maximum in winter and minimum in spring. Heavy metal results showed no seasonal pattern.