A modified drop-net method for sampling mobile epifauna on marine shallow sandy bottoms
| Autor: | Bo Tallmark, Sverker Evans |
|---|---|
| Rok vydání: | 1979 |
| Předmět: | |
| Zdroj: | Ecography. 2:58-64 |
| ISSN: | 1600-0587 0906-7590 |
| DOI: | 10.1111/j.1600-0587.1979.tb00682.x |
| Popis: | The seasonal variations in numbers and biomass of the mobile epifauna of a shallow, sandy bay in Gullmar Fjord (Sweden) was investigated during 1976–1977 using the drop-net technique. Juvenile plaice, Pleuronectes platessa L., sand goby, Pomatoschistus minutus (Pallas), and brown shrimp Crangon crangon L. are the dominant epifaunal species. A net enclosing an area of 100 m2 was used, and the organisms captured were collected with a small trawl. Three stations with a water depth≤ 1 m were regularly sampled with a total number of 73 drops. Maximum abundance was for plaice in June (6 ind m-2), for the shrimp in July-August (61 ind m-2), and for sand goby in September (2 ind m-2). Standing stocks (dry wt) were 0.2, 1.5 and 0.2 g m-2 respectively. Production estimates were based on seasonal changes in size frequency and information on specific growth rates. The production rate was for plaice (0-group) 0.3 g m-2 yr-1, for the shrimp 1.5, and for sand goby 0.2 g m-2 yr-1. Reliable estimates of the absolute abundance can be derived from the mean catch per unit area only when the efficiency of the fishing gear is known. After 6 hauls with the trawl in the drop-net enclosure more than 85% of the shrimps were caught and after the fifteenth haul less than 1% were still left. The fishing efficiency of a push-net in relation to the drop-net was for the shrimp 50%, for plaice 35% and for sand goby 17%. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|