I used to go to the Ballard Locks as a child and watch the salmon swimming up the fish ladder. There were always so many of them! So active and so beautiful. My parents told me these ladders help salmon navigate around the Locks which were obstructing their natural migration pattern up the river. Childlike optimism had me in awe of these things and blinded to their complexities, but now that I’m older I’m better able to understand their damages. When you’re a kid it’s easy to be blindly optimistic, but naming the damage and acknowledging the root of our problems are important steps in overcoming the hurdle that this over-optimism imposes, and to make some sort of change.
Now, the salmon are dying and our anthropogenic impact is the sole reason why. Climate change, dams, hatcheries, fisheries, and other aquatic disturbances are making their environments uninhabitable, resulting in an unprecedented population decrease (1).
Salmon hatcheries are a human cultivated response to overfishing. The thought is that by raising salmon in a benign environment and then depositing them in their natural environment we are increasing the likelihood of juvenile survival and ultimately replenishing the population. Just like the optimism that salmon ladders gave to me in my childhood, the story of hatcheries similarly comes off as helpful, not harmful, to the species. Hatcheries impact the genetic makeup of the salmon to be adaptive against human capture, and maladaptive for actually living as a salmon. Specifically, captive salmon are pressured to lay many small eggs rather than fewer large eggs (2). Large eggs survive better in the wild but hatchery conditions are benign so both large and small survive equally. Hence we are genetically prioritizing our human desires (many small eggs) over the salmon’s necessities (a few large eggs).
Ultimately, hatcheries create adaptations that are beneficial in captivity and maladaptive in the wild. Domestication selection is the evolutionary process where humans unintentionally select against the desired traits in species by collecting and killing the animals in that species who present those traits (1). Domestication selection is thus the genetically based result of our exploitative desires. Humans are attracted to large salmon; by catching large salmon, we are impacting the collective salmon population to grow smaller to resist being caught. However, wild salmon generally have better survival rates at larger sizes. This response is not an intentional impact, often it is unintentional, but the point remains: by relying so heavily on a species we are causing it to change for us, rather than itself.
Genetic variation is essential to evolution, without different possibilities of genes to choose from they’re unable to evolve (3). This is what we need to implement: variation. At least some of us need to deviate from our fantasy of a perfect ecosystem, really think of the direct and indirect consequences of our interventions, and actively choose to say no to the desires of the human for the sake of the non-human. Without some variation of response, I worry we will be blinded by this false optimism I’ve experienced before, unable to evolve. I for one refuse to live in a world without salmon, so let’s get it together!
References:
- Kuparinen A, Festa-Bianchet M. 2017 Harvest-induced evolution: insights from aquatic and terrestrial systems. Phil. Trans. R. Soc. B 372: 20160036.
- Heath, D. D. Rapid Evolution of Egg Size in Captive Salmon. Science 299, 1738–1740 (2003).
- Sultan S, personal communication, March 31, 2020
