“The knee-bone’s connected to the thighbone…” — from the spiritual “Dem Bones”
Sometimes, it’s reading between the lines that’s most interesting.
In recent months, there’s been greater focus on declining shrimp stocks and the effect that returning cod numbers might be having on that decline.
You could, of course, jump right to the conclusion that growing numbers of cod, as shrimp predators, are the whole issue.
Not really. After all, cod has a rightful place in the ecosystem. Consider this, from the latest DFO science report on shrimp stocks: “Predation on shrimp, and the associated predation mortality rate, showed an increasing trend until 2011, and has decreased since. This decrease is associated with an increase in consumption of capelin by predators in conjunction with the combined biomass of shrimp predators remaining relatively steady since 2011. Shrimp is an important forage species, particularly when there is scarcity of high energy prey such as capelin.”
So, is the issue with shrimp a matter of too many cod, or too few caplin?
“The ratio between predation and shrimp biomass is a relative index of predation mortality and is currently around double the level in the mid-1990s and 2000s. Shrimp predation mortality in the near future is expected to remain high unless abundance of alternative prey increases,” the report says.
Over to you, caplin.
Caplin stock assessments used to be done every year — then, the span stretched to every two years. The last one, in 2015, pointed out that, although numbers were strengthening, fish stomach contents indicated they were having a difficult time finding food.
“Given the poorer environmental and feeding conditions seen in 2014, coupled with the below average strength of the 2014 larval cohort, and the importance of capelin as a forage species, it is suggested that a cautious approach to increasing total allowable catches be adopted,” the report said.
Caplin science is already pretty thin on the ground: it’s fair to say that there’s plenty we don’t know about the important little fish.
The Standing Committee on Fisheries has recommended DFO go back to annual surveys, but that’s not really enough. It’s like trying to put together a puzzle without having the pieces.
The report on shrimp points out that stock assessment has to be based on more than “how much can we safely catch?” — the current fisheries management structure.
“For ecosystem-based management … ‘harvest’ would be replaced by some combination of harvest and ecosystem function,” the report says.