fish, oceans, conservation
I agree this is abnormal, scary and likely chemically-induced, but fishing impacts have also caused changes to salmon genetics and sexuality:"Documented fishing-induced genetic impacts to salmon include increasing the percentage of smaller jack males spawning, greatly decreasing the average size of spawning males (and females)overall, and decreasing the average size of salmon caught in most fishieries. Predicting with any certainty the long-term impact on these traits and trade-offs is impossible, but it is clear that humans already have and are continuing to profoundly alter these and likely other salmon traits thorugh fishing and other activities. Furthermore, human activity is rapidly altering the marine, estuarine, and freshwater environments on which salmon (and other species) depend. Such alterations can also be expected to produce long-term evolutionary changes in the proportion of males maturing as jacks. Research suggests that in some cases male salmon populations once characterized by large, aggressive, fighting, hooknose males may be transformed into ones dominated by much smaller, precocious jacks. A variety of other outcomes is also likely, and it is entirely possible that in the future, ocean caught salmon will consist solely of females." (For more info, see pages 81-83 in the book Marine Reserves: Science, Design, and Use; Sobel and Dahlgren, 2004; and articles by Mart Gross, 1985, 1988, and 1991 in Nature, Science, and Ecology).
I've seen evidence of increased "residualization" of salmon (males staying in rivers and never migrating, then spawning as trout-sized "jacks"). This seems to happen where good habitat is available in spawning streams but migration is hazardous due to dams, poor water quality, etc. Is this evolution in action?
I've been studying fate and effects of lost lead fishing sinkers on WQ in midcoast Oregon salmon streams. Freshwater mussels (Margaritifera falcata) are long-lived and can record a timeline of bioavailability history of metals on a site-specific basis. Other pollutants may be similarly recorded if we can learn how to read the clues. Lead, cadmium, and methylmercury NPS pollutants can affect many of the same physiologic pathways and thus become additive and even synergistic. Freshwater habitat can then have generally unrecognized limiting factors for salmonid diversity recovery. Some of these effects can leave fish looking 'normal' in the hand, but less than what they need to be to survive in the competition at near-ocean-entry.Some of these effects can probably be genderbending, especially when combined with PCB effects commonly contaminating salmon.
Thanks Ray, it's sad to hear that such harm can come from seemingly innocuous things like lost fishing sinkers. Devastating harm that is hard to detect is VERY hard to address.
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