FISH can smell out their enemies. And salmon are more aggressive towards
those who don鈥檛 smell like family, say Scottish scientists.
鈥淚t is possible that salmon use scent to mark their territory,鈥� suggests
biologist Si芒n Griffiths of the University of Glasgow. 鈥淭hey may interpret
high concentrations of odour from unrelated fish as a threat.鈥�
Previous evidence suggests that Atlantic salmon (Salmo salar)
identify family members by their body odour. Now a new study by researchers at
the University of Glasgow and the Freshwater Fisheries Laboratory in Pitlochry
shows that salmon sniff out unrelated fish and behave aggressively towards
them.
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The researchers raised 44 salmon from two different families and compared
their behaviour in tanks through which water flowed once, and tanks in which the
water was recirculated. Recycling the water concentrated the fish鈥檚 scent.
They measured the frequency of aggressive interactions such as erecting fins,
attacking and biting. In recirculated water, aggression flared twice as often
between unrelated fish as it did between siblings. In once-through water, the
levels of aggression among related and unrelated fish were similar.
Griffiths, who reported her results at the Edinburgh International Science
Festival this week, says that the findings could be of use to wild fisheries
managers. To reap the benefits of raising siblings together, she says, they
should avoid fast-flowing streams and use eddies or pools in which body scent
would be intensified.