Publication Abstract

Title
The role of the pectoral fins in station holding of Atlantic salmon parr, Salmo salar
Publication Abstract

Short Communication: The role of pectoral fins in station-holding of atlantic salmon parr (Salmo salar L.)

G.P. Arnold, Paul W. Webb and B.H. Holford

Benthic fish resist downstream displacement in a current by balancing drag, the force orientated downstream, with the friction force. The friction force is ,u(Wo-L), where y is the friction coefficient, Wo the weight force of the fish in water (N), and L the lift force (N) acting on the body and fins (Arnold and Weihs, 1978). Above a critical speed, friction is insufficient to counteract drag and the fish must either swim or seek shelter from the flow. This note reports tests of the commonly proposed hypothesis (e.g. Kalleberg, 1958; Keenleyside and Yamamoto, 1962; Jones, 1975; Wankowski, 1981) that the pectoral fins are important to station-holding in Atlantic salmon, acting as hydrofoils generating negative lift.

Parr were obtained by electrofishing in the River Frome and were transported by road to Lowestoft in insulated containers. Fish were held in tanks with an underwater gravel filter, continuously aerated and flushed with water at 10-11'C. Parr were fed daily on chopped fish.

Station-holding parr were observed in a flume (Arnold, 1969) on both a smooth (Perspex) and a rough substratum. The rough substratum was subrounded gravel (mean diameter 5.2±0.8mm; mean±2S.E.). Telecentric, parallax-free photographs (Arnold and Nuttall-Smith, 1974) were taken of parr holding station on Perspex. A dye stream injected just upstream of the pectoral fin was also photographed. A lateral viewing, rigid Endoprobe (Inspection Instruments Ltd,) was used to take head-on photographs. The probe had a field of view of 30° and could focus from 4 mm to infinity. Parr used in these experiments averaged 127 ±13 mm in total length.

The function of the pectoral fin was tested by comparing station-holding performance of intact parr (length 122±16 mm) and parr from which the pectoral fins had been amputated (length 115±14mm). Parr were anaesthetized in 0.5 ml l-1 phenoxyethanol and either the pectoral fins or part of Me dorsal and adipose fins were amputated.

Reference:

G.P. Arnold, Paul W. Webb and B.H. Holford, 1991. Short Communication: The role of pectoral fins in station-holding of atlantic salmon parr (Salmo salar L.).Journal of Experimental Biology, 156: 625-629.

Publication Internet Address of the Data
Publication Authors
G.P. Arnold*, P.W. Webb and B.H. Holford*
Publication Date
January 1991
Publication Reference
Journal of Experimental Biology, 156: 625-629
Publication DOI: https://doi.org/