Scientific argument
Scientific argument
Support banning scuba spearfishing
Nearly all tropical countries have banned the use of spearfishing with scuba because viable fisheries cannot be maintained if the removal of the breeding stock of larger fishes becomes too thorough. Spearfishing while free-diving is an honorable sport and a viable fishery can be maintained, but the added technology of scuba allows the fishers to be selective in targeting the larger fishes and it can be very effective in targeting sleeping parrotfish and other species at night.
Studies of hundreds of species of fish have demonstrated that when the age or size structure of a fish population is shortened by selective removal of larger individuals, then population replenishment seriously declines, becomes sporadic, and the fisheries population loses resilience and sustainability.
Spearfishing with scuba can have a great effect on the sustainability of fisheries by selectively targeting the larger fish which can lead to the exponential reduction in the number of eggs and larvae produced, and shorten the population’s reproductive season.
How does effectively catching large fish have a greater impact on population replenishment than several times the total weight of medium-sized fishes? Because, in nature, the fertility of the females goes up greatly with age. It has been measured that one large, 24-inch snapper has the same fecundity as 212 medium-sized 16-inch snappers. Taking only one big one has the same effect on the sustainability of the population as taking 212 medium sized ones.
In the modern world, people tend to be disconnected from nature and want the glory of taking a big one and don’t think about the sustainability of the harvest or the value of leaving the big ones behind to breed.
The renowned marine scientist Robert Johannes spent much of his career learning the wisdom of the elder fishermen in Micronesia, with regard to resource management. He pointed out the wise elders could see through the complex interactions and unpredictable recruitment patterns in assessing the state of their fisheries resources with straight-forward observations as to whether the big ones were still there. Movies by Louis K. (Buzzy) Agard show there was an abundance of large fishes on Hawaii’s reefs immediately following World War II. But this was before the time scuba arrived and the large ones have substantially deceased since fishers have been given the power of high technology scuba.
In addition to reducing the sustainability of the fisheries, taking a substantial portion of large parrotfish can have serious detrimental effects on the coral reef ecosystem. Larger parrotfish actually scrape the substratum when removing seaweed, thereby keeping the seaweed under control and facilitating coral growth for healthy systems. Smaller parrotfish are relatively ineffective and so the decrease in large parrotfish in Hawaii can lead to an increase in seaweed and the resulting degeneration of the Hawaiian coral reef ecosystem.
For both the viability of parrotfish populations and the health of coral reef ecosystems, we must not allow scuba to be used with spearfishing. In the late 1970s, I observed the elimination of the large humphead parrotfish Bolbometopon muricatum from Guam. They were spectacular to observe until they were removed by commercial spearfishers when they began using scuba. The same was observed in American Samoa, when commercial fishers began to use scuba.
I have heard several times in Micronesia and in American Samoa, the fishers say, “Our resources do not belong to us, we are borrowing them from our children and our future generations.”
This is why most other countries and coastal villages allow spearfishing by freediving, but prohibit the use of high-technology scuba.
Chuck Birkeland, Ph.D.
Waipahu, Oahu