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Journal of Experimental Marine Biology and Ecology 242 1999 95–106
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The swimming behaviour and distribution of Neomysis integer in relation to tidal flow
a b
a , b
S.M. Lawrie , D.C. Speirs , D.G. Raffaelli , W.S.C. Gurney ,
c d
D.M. Paterson , R. Ford
a
Culterty Field Station , University of Aberdeen, Newburgh, Ellon, Aberdeenshire AB41 6AA, UK
b
Department of Statistics and Modelling Science , Strathclyde University, Livingston Tower, Glasgow, UK
c
Gatty Marine Laboratory , University of St Andrews, St Andrews, Fife, UK
d
Department of Marine Sciences , University of Otago, Dunedin, New Zealand
Received 11 April 1999; received in revised form 29 June 1999; accepted 2 July 1999
Abstract
The behaviour and distribution of the estuarine mysid shrimp, Neomysis integer , were
investigated in relation to a variety of flow regimes in the field and in the laboratory. In the field, Neomysis aggregated in low-flow areas, such as in the lee of rocks and macroalgal clumps. Over
the low-tide period and during ascending and high-tide periods, individuals were concentrated in a band toward the moving tide edge where flows are typically low. Experiments performed using a
laboratory flume demonstrated a clear response of Neomysis to flow, the proportion of individuals
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above the bed declining with increasing flow. At flows of up to 10 cm s , 90–95 of individuals
were able to maintain position on the bed of the flume, but at flows greater than this, Neomysis were unable to maintain position. When provided with a choice of water depths in a laboratory
static tank zero flow, there was little evidence of depth-seeking behaviour. We suggest that avoidance of areas of high flow is a key factor determining the local distribution of Neomysis
.
1999 Elsevier Science B.V. All rights reserved.
Keywords : Behaviour; Current; Mysids; Neomysis integer; Aggregation
1. Introduction
In common with many other mysid shrimps, Neomysis integer shows aggregation behaviour Clutter, 1969; Mauchline, 1971; Dadswell, 1975; Parker and West, 1979;
Ohtsuka et al., 1995. The form of these social aggregations, their placement and their
Corresponding author. 0022-0981 99 – see front matter
1999 Elsevier Science B.V. All rights reserved.
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.M. Lawrie et al. J. Exp. Mar. Biol. Ecol. 242 1999 95 –106
function, have been discussed at length and seem to vary from species to species Berrill, 1968; Clutter, 1969; Mauchline, 1971; Dadswell, 1975; O’Brien, 1988; Ohtsuka
et al., 1995. In the case of Neomysis integer , which is restricted to estuarine habitats,
one explanation of aggregations may be that individuals move to areas of the estuary where they are less likely to be displaced Parker and West, 1979; Hough and Naylor,
1992; Roast et al., 1998. Within the Ythan estuary, Aberdeenshire, Scotland, aggregations appear most obvious
at the tide edge during the rising, falling and high-tide periods, but during the low-tide period are most conspicuous in the lee of rocks and macro-algal clumps, or as a
mono-layer in shallow water at the sediment–water interface. These patterns of distribution suggest that aggregations may be more common in low-flow areas, but the
relation between flow and abundance has not been quantified in the field to date at the relevant small scale cf. Roast et al., 1998. In addition, it is not clear to what extent the
distribution of aggregations is an inevitable consequence of passive entrainment of individuals into such low-flow areas, or whether Neomysis actively seeks such
conditions. In the present paper, we address these questions by recording the abundance of Neomysis at different states of the tide in relation to water depth and flow, and by
observing the response of Neomysis to flow under controlled laboratory conditions. Roast et al. 1998, have recently described the activities of Neomysis under a range of
conditions within a laboratory annular flume and they relate these to the physical environment of the Looe estuary, Cornwall, UK. In the present study, we were able to
make contemporary estimates of Neomysis densities and the flow environment in the field, and also to relate these to behavioural observations in a much larger flume
environment. Our work thus both compliments and extends that of Roast et al. 1998.
2. Materials and methods
