Is there any consensus within EA / adjacent animal welfare communities about the ethics of eating line-caught carnivorous fish?
(For context I've been strictly vegetarian and mostly vegan for a while now, but am thinking about adding mussels back into my diet and am wondering about line-caught carnivorous fish.)
No consensus as far as I know, but there's Trophic Cascades Caused by Fishing (Brian Tomasik, 2015). Summary:
One of the ecological effects of human fishing is to change the distribution of prey animals in the food web. Some evidence suggests that harvesting of big predatory fish may increase populations of smaller forage fish and decrease zooplankton populations. Meanwhile, harvesting forage fish directly (to eat as sardines/anchovies or to feed to farmed fish, pigs, or chickens) should tend to decrease forage-fish populations and increase zooplankton populations. On the other hand, it may also be that harvesting more fish reduces total fish biomass in the ocean, without significantly increasing smaller fish populations. There are many other trends that might be observed, and generalization is difficult.
