| Abstrakt: |
Fish abundance and environmental data collected over ten years (1980-1989) from the middle Thames estuary, England, were analyzed to detect temporal trends in fish populations and relationship with environmental parameters, and to assess water quality. Fish were collected from the cooling water intake screens of West Thurrock power station, situated 35.5 km below London Bridge, in the mid-estuary. Marine species abundance were highly seasonal, with peaks in December-March for herring (Clupea harengus), sprat (Spmfm sprattus), 3spined-stickleback(Gasterasteus aculeatus), and poor cod (Trisopterus minutus); July-August for flounder (Platichthys fleSus); and September-December for sand goby (Pomatosdtistus minutus), whiting (Merlangius merlangus), bass (Dicenharchus labrax), plaice (Pleuronectes platessa), and dab (lamanda limanda). Bimodal seasonal patterns of peaks or unclear seasonality in abundance characterized marine estuarine-dependent sole (Solea solea), Nilsson's pipefish (Syngnathus rostelattus) (April/May and September/October), and pouting (Trisopterm luscus) (May and November/December); the estuarine smelt (Osmerus eperlanus) (October and January) and the catadromous eel (AnguiUa anguiUa) (June and October). There was substantial variation in the abundance of common species overthe period of ten years, with herring, sand goby, flounder, and plaice showing a stable abundance in 1980-1984, increasing sharply in 1985-1986, and then decreasing successively through the remainder of thedecade (1987-1989). The first half of the decade was a period of higher abundance for less tolerant species such as smelt, sprat, and poor cod, while the second half showed higher abundances of species tolerant to harsh environmental conditions such as sand goby, flounder, eel, and plaice. A general pattern of stable fish populations with a slight trend of deterioration was found to emerge over the years, related to the number of species and quantities of common species. Multivari [ABSTRACT FROM AUTHOR] |
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