July 7, 2017 — The interaction of predators, fishing and forage fish is more complicated than previously thought and that several factors must be considered, says researcher.
The group of researchers was evaluating the interaction after results from an earlier report found that fishing of forage species had a large effect on predator population, said the Marine Ingredients Organization (IFFO). Those harvested fish are used in several areas including as feed ingredients.
The new study was initiated because there were some questions regarding the methods used in the initial project, said Ray Hilborn, with the school of aquatic and fishery sciences at the University of Washington and corresponding author.
“When the original Lenfest [Forage Fish Task Force] report came out, a few of us said it seemed that the methods they were using were not up to the questions they were asking,” he told FeedNavigator. The report also offered several policy recommendations, he added.
“It was on our radar screen,” he said. “And one of the things I’ve been interested in looking at is the intensity of natural fluctuation in populations, and forage fish are notable for how much they vary naturally.”
The interaction between forage fish populations and predators is more complicated than may have been suggested by earlier studies tracking that relationship, and several factors need to be considered when analyzing the role that fishing plays on that relationship, he said. “The key point isn’t that there isn’t an impact, but that you have to argue case-by-case,” he added.
Several factors need to be considered when assessing the interaction among predators, forage species, and fishing of those forage species, the researchers said in their study. “We show that taking account of these factors generally tends to make the impact of fishing forage fish on their predators less than estimated from trophic models,” they added.