TY - JOUR
T1 - How strong are familiarity preferences in shoaling fish?
AU - Barber, Iain
AU - Wright, Hazel A.
N1 - Funding Information:
We are grateful to the Association for the Study of Animal Behaviour, who funded this research through a summer scholarship award to H.W., and two anonymous referees who provided helpful comments on the manuscript. I.B. was in receipt of a NERC research fellowship during the study. We thank John Laurie, Raellie Patterson and Jen Andrew for technical assistance, and the Fish Biology Group at Glasgow University for comments on the work.
PY - 2001
Y1 - 2001
N2 - Individual fish of certain species show preferences for rejoining shoals of familiar individuals, suggesting that the development of familiarity within groups may be beneficial to group members. However, the relative value of shoaling with familiar individuals compared to, for example, joining a larger or more phenotypically matched group, is not known. We first confirmed, in separate experiments, that European minnows, Phoxinus phoxinus, prefer to join shoals of familiar individuals (with which they had been kept for 14 days) over unfamiliar ones, and show an increasing preference for the larger of two unfamiliar shoals presented in numerical size ratios of 1:1, 1:1.2, 1:1.9 and 1:4. In the latter experiment, test fish showed a marginal preference for the larger shoal at size ratio 1:1.2, and significant preferences in the 1:1.9 and 1:4 trials. To examine how test fish traded off familiarity against group size, we used the same shoal size ratios in a third experiment, this time with the smaller shoal being composed of individuals familiar to the test fish. In these trials, preferences for larger (nonfamiliar) and smaller (familiar) groups were balanced at the 1:1.9 shoal size ratio, and test fish significantly preferred the larger shoal only in the 1:4 trials. This suggests that the fish perceive the value of shoaling with familiars as equivalent to the benefits gained by doubling shoal size. Our results also indicate that preferences for familiar shoalmates are sufficient to offset defection to slightly larger groups. We discuss how this may stabilize group composition in natural habitats.
AB - Individual fish of certain species show preferences for rejoining shoals of familiar individuals, suggesting that the development of familiarity within groups may be beneficial to group members. However, the relative value of shoaling with familiar individuals compared to, for example, joining a larger or more phenotypically matched group, is not known. We first confirmed, in separate experiments, that European minnows, Phoxinus phoxinus, prefer to join shoals of familiar individuals (with which they had been kept for 14 days) over unfamiliar ones, and show an increasing preference for the larger of two unfamiliar shoals presented in numerical size ratios of 1:1, 1:1.2, 1:1.9 and 1:4. In the latter experiment, test fish showed a marginal preference for the larger shoal at size ratio 1:1.2, and significant preferences in the 1:1.9 and 1:4 trials. To examine how test fish traded off familiarity against group size, we used the same shoal size ratios in a third experiment, this time with the smaller shoal being composed of individuals familiar to the test fish. In these trials, preferences for larger (nonfamiliar) and smaller (familiar) groups were balanced at the 1:1.9 shoal size ratio, and test fish significantly preferred the larger shoal only in the 1:4 trials. This suggests that the fish perceive the value of shoaling with familiars as equivalent to the benefits gained by doubling shoal size. Our results also indicate that preferences for familiar shoalmates are sufficient to offset defection to slightly larger groups. We discuss how this may stabilize group composition in natural habitats.
UR - http://www.scopus.com/inward/record.url?scp=0034993822&partnerID=8YFLogxK
U2 - 10.1006/anbe.2000.1665
DO - 10.1006/anbe.2000.1665
M3 - Article
AN - SCOPUS:0034993822
SN - 0003-3472
VL - 61
SP - 975
EP - 979
JO - Animal Behaviour
JF - Animal Behaviour
IS - 5
ER -