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Putting the big ones back

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Thoughts on Snapper Fishing: Putting the biggest ones back

Snapper Goat Island by Roger GraceIn the simplest terms, we release the biggest snapper because these are the best breeders. We’ve all heard that before, but what does it actually mean? 

This layman’s summary has been initiated by a number of comments made recently by local fishermen about snapper fishing during spawning season. More specifically it is a result of an article in the Taranaki Daily News on 16/11/2010 about one man’s prize-winning snapper. An online debate ensued splitting “fishos” and “greenies” into two firm camps with abusive comments hurled every which way. Here we attempt to explain from a sensible, logical viewpoint why there needs to be balance in our approach to fishing so that we actually have fish forever. 

 

What are the reasons for releasing the big snapper? 

We’re back to the big ones being the best breeders. Not only does egg production increase exponentially with greater size, but also big snapper tend to spawn several times during a season, whereas smaller ones may spawn only once. In other words, the bigger the snapper, the greater the number of eggs and the greater the probably of that number of eggs being produced more than once in a season. That equates to an optimum number of juveniles bolstering the snapper population. But this is only the start of the story. As well as producing more eggs, the offspring of a large snapper are better examples of the species. By definition a large snapper is also a “good snapper” – it is a skilled predator and both smart and fast enough to have avoided our fishing lines over the years. It follows that these good snapper are the key breeders passing on the best genes to the population. 

This brings us down to the principle of natural selection. The species depends on these various forms of natural selection to prosper and evolve in a changing world. By fishing out the biggest snapper we compromise the evolutionary development within the population. Over time there will be changes in the snapper population – unnatural or artificial selection, if you like - that are not in the interest of the species. The good genes will be lost. 

How does this relate to areas of 100% protection?

Snapper by Roger GraceUnfortunately there are other unknowns that come in to play to further confound the question. The science we base these facts on is only what we know and of course, we don’t know what we don’t know. Fishing is essentially an uncontrolled experiment. The upshot of this ‘unknown’ is that it is crucial from a scientific standpoint to have a network of 100% protected zones covering representative habitats in order to establish a “control”. One of the principles of scientific experimentation is that when you conduct an experiment which involves manipulating something (in this case, fish populations – specifically snapper) you run a "control" for the experiment in which you deliberately avoid that manipulation (i.e. no fishing) just to check what happens in the absence of that manipulation. The bottom line is that we don’t know enough about the different ecological roles snapper play at different sizes. However, we do know from other species (Pacific Salmon, for example) that by taking out too many of one type you remove the role that this type plays in the system, which translates to many other effects. Often we don’t know much about these interactions and will only see results when it’s too late. 

 Do we want to take that risk?

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