17 Mar 2014
Ms Bellinger says hatcheries may no longer be of use for conservation of trout. Photo: Shelly Hanks, WSU Photo Services
A recent study by researchers at Washington State University (WSU) suggests trout hatcheries could be interfering with the appearance and behaviour of domestic trout, making them inferior to their wild relatives.
“The use of hatcheries to support declining wild salmon and steelhead is controversial,” said Kirsty Bellinger, who carried out the study. “They have a role as being both a part of the solution in supplementing depleted stocks and as being a hindrance to boosting natural populations, as they often produce fish that look and behave differently from their wild relatives.”
The study, which used a ‘speed trap’ for fish and a 1m long plastic tank filled with water and fitted with electronic sensors, revealed dramatic differences in the swimming ability of domesticated trout and wild trout.
Over 10 weeks, 100 genetically similar hatchery-raised and semi-wild rainbow trout were run through the tank, while their speed was clocked and their growth monitored from week to week.
“The highly domesticated fish have bigger body sizes but slower swim speeds compared to the more wild lines that are smaller. It is intuitive to think that the more you feed them, the more they’re going to grow, the faster they’re going to be, and that’s what we see within each clonal line. However, between the lines, the domesticated fish were larger but slower sprinters,” she added.
Over the past century, hatcheries have become a mainstay of recreational fishing, providing millions of trout and other salmonoids to lakes and streams. More recently, hatcheries have come to be seen as tools in conserving native stocks.
The State of Washington has more than 200 hatcheries, with most producing salmon and steelhead, and ocean-running trout, and about one-fourth producing trout and other game fish.
“Fish managers want the biggest bang for their buck,” explained Ms Bellinger. “But if increased size is a tradeoff of sprint speed, as our data show, then we assume hatchery fish are being picked off by predators due to their slower speed, which makes the process of supplementing native fish with hatchery fish an inefficient tool for conservation and waste of money.”
Video: Washington State University
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