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more on CA DFG’s conversion to triploids: all of California’s stocked rainbow trout soon to be dumb(er)?

Just last week we posted that nearly all of California’s hatchery-raised rainbow trout will be triploids within two to three years.

Now we can’t help but wonder what it really means.

According to U.K. Salmon and Freshwater Fisheries Consultant David J. Solomon:

Apart from having three sets of chromosomes, as opposed to the usual two in trout, there are a number of other relevant differences [between diploid and triploid trout].

Many organs and tissues have larger but fewer cells in triploids, including the brain, muscle, retina, liver and kidney (Benfey, 1999). This appears to arise because the extra set of chromosomes dictates an increase in cell nucleus dimensions which in turn affects overall cell size.

Fewer brain cells doesn’t mean will mean you’ll hook a triploid trout on every cast, particularly if diploid trout (with the normal chromosomal configuration) are present in the same water. Solomon goes on…

However, this rather fundamental difference appears to have remarkably little knock-on effect upon physiology, behaviour and general performance. Development rates appear very similar, until the onset of sexual maturity in diploids. Diet utilisation and energetics appear unaffected. Triploids are generally less aggressive than diploids, which leads to poorer performance when the two are reared together in intensive culture – but these differences disappear when the two are reared separately.

It’ll be interesting…