Think­ing Straight

I am a com­mon­sense kind of guy. I’m pretty sure the sun will rise to­mor­row in the east and will keep that up un­til, in the words of Shake­speare, I “shuf­fle off this mor­tal coil.”

Saltwater Sportsman - - Tod / Conservation - By Rip Cun­ning­ham

It also seems to be com­mon sense that in the nat­u­ral world there are preda­tor and prey re­la­tion­ships that have de­vel­oped over tens of thou­sands of years. Mankind’s ef­forts to dis­rupt those re­la­tion­ships with our on­go­ing ex­ploita­tion of fish­eries world­wide are only a blink of the eye at the end of that times­pan.

In the world of fish, it seems that the re­la­tion­ship of preda­tor to prey is pretty straight­for­ward. There are some preda­tors (fish and other crit­ters that eat smaller fish), and there are lots and lots of prey (the lit­tle ones that get eaten). There are many rea­sons this has de­vel­oped this way. The pri­mary ones are that there are lots of prey be­cause the preda­tors need to eat and be­cause there is safety and longevity in num­bers. Pretty darn sim­ple to a com­mon­sense kind of guy.

Then ear­lier this year, a study came out that, to a great ex­tent, turns this sim­ple the­ory on its head. The study was done by a group of fish­eries bi­ol­o­gists who have a long list of let­ters after their names. So, who am I to ar­gue with all that knowl­edge? Com­mon sense says I should not, and com­mon sense says I should. I’ll fol­low com­mon sense!

The study is called “When does fish­ing for­age species af­fect their preda­tors?” For those in­ter­ested in read­ing it, you can find it at: sci­encedi­rect.com/ sci­ence/ar­ti­cle/pii/s0165783617300176. The study was con­ducted by seven highly re­garded re­searchers. If the or­der of their list­ing in the doc­u­ment has any mean­ing, then Ray Hil­born PH.D. ap­pears to be the lead re­searcher. There are a num­ber of con­clu­sions from the study, but for me the most im­por­tant are: The preda­tor rate of in­crease is un­cor­re­lated with for­age fish abun­dance; for­age species are af­fected much more by en­vi­ron­men­tal con­di­tions than by fish­ing; and preda­tors of­ten take small for­age fish that are un­af­fected by fish­ing.

I have to say that I ques­tion the first con­clu­sion, as it just does not pass the “com­mon sense” smell test for me. For any­one get­ting a de­gree in marine biology, the trophic pyra­mid has to be one of the ba­sic build­ing blocks.

Think­ing Straight

The fish at the top are the apex preda­tors, and those at the bot­tom are the for­age. Those of us who fish likely fo­cus on the sport-fish apex preda­tors, but there are many dif­fer­ent kinds that make up the ecosys­tem. We know that if you take away all the for­age, there will be no preda­tors. With that as a ba­sis, there has to be a direct cor­re­la­tion be­tween these two parts of the trophic pyra­mid. Can some level of re­moval be tol­er­ated by this re­la­tion­ship with min­i­mal im­pacts? This re­search says it can, but the ques­tion be­comes: Where is the tip­ping point? How do you ac­count for all the eco­log­i­cal ser­vices pro­vided by the for­age?

Again, it seems to be com­mon sense that for­age can be af­fected more by en­vi­ron­men­tal con­di­tions than by fish­ing. We see this ev­ery year with some species seem­ingly dis­ap­pear­ing only to reap­pear again in fully re­stored num­bers. The nat­u­ral world works this way, but that process evolved in a world where man had lit­tle or no im­pact. Should removals be done at the high­est level pos­si­ble or at some lower pre­cau­tion­ary level? Both fish­ing and en­vi­ron­ment im­pact for­age, but we can only con­trol fish­ing removals.

The pri­mary ex­am­ple used to support the con­clu­sion that preda­tors usu­ally take small for­age that are un­af­fected by fish­ing is one that I have some level of fa­mil­iar­ity with. They based this con­clu­sion on a study of the stom­ach con­tents of striped bass, which showed that the bass ate pri­mar­ily ju­ve­nile men­haden. Re­ally? It must have been blind luck catch­ing all those big striped bass on large men­haden year after year. At cer­tain times of the year, ju­ve­niles will be pre­dom­i­nant, but not all year. And last time I checked, it takes the big ones to make small ones, so there is an im­pact on ju­ve­niles from adult removals.

This re­search, to a great ex­tent, was con­ducted to counter re­search done by the Len­fest Ocean Program called Lit­tle Fish, Big Im­pact: ocean­con ser­va­tion­science.org/for­age­fish/files/ Lit­tle %20 fish ,%20 big %20 im­pact. pdf. The Len­fest re­search used tra­di­tional trophic mod­els that the new re­searchers said did not ac­count for nat­u­ral vari­a­tions. I will let the Ph.d.s point fin­gers at each other, and I will re­turn to com­mon­sense think­ing. Was the new re­search done to support the for­age­ex­trac­tion in­dus­try, or was it done out of pure cu­rios­ity? Most be­lieve the former. Truly valu­able re­search is done with­out con­clu­sions be­ing pre­de­ter­mined or de­sired.

Does this mean there should be no fish­ing extraction of for­age fish? Not at all. But un­til sci­ence can de­ter­mine and quan­tify all the ecosys­tem roles filled by for­age fish, the fish should be man­aged un­der the “pre­cau­tion­ary prin­ci­ple.”

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