Spearfishing is new and makes it easy to catch fish that are important for the reef to stay healthy

Science commentary 3

Spearfishing is a newer way of fishing in the outer islands. Many young people like to spearfish because you can catch big fish, it can be fun and exciting, and it works well. However, spearfishing was not a traditional way to fish, so when it began, the old ways of doing things did not work well to control how spearfishing affected the reef and fish. With spearfishing, the fisher can choose to only catch the types of fish they prefer (and usually the bigger ones of those species). Most of the fish caught by spearfish on the Yap outer islands are herbivorous fish (algae-eating fish) such as surgeonfish (like Morfach) or parrotfish (especially at night) like Row and Mau–dilmow.

Catching too many of these fish can be bad for reefs and people because:

●      Too much algae means not enough coral

Morfach eat algae (ocean plants), and especially new algae (also called “turf algae") as it starts to grow on a reef, and they even eat films of bacteria. Too much of this kind of algae and bacteria can be bad for the reef and make the water dirty. Baby corals, which are important to the health of reefs, can’t grow where there is a lot of algae and bacteria. So if there are not enough fish like Morfach, the coral reef can suffer, and so can all the other fish. If there are not enough Morfach, too much of this young algae (also called turf algae) will grow. Mau (parrotfish) also eat algae, but usually larger (macro) algae, and the bacteria that grow on the algae and corals. These larger algae also keep corals from growing. So these fish keep reefs ‘clean’ and help corals grow, which brings in other fish. These are all tied together to make a healthy reef, which supports healthy people!

●      Taking all the big fish means not enough babies

Spearfishers often choose the largest fish. In parrotfish (Row and Mau) this usually means male fish, because parrotfish change their sex as they grow. They are born as female and then become male. One bigger male Row or Mau will mate with many females, and so bring many babies to the reef to keep it healthy (and to feed people). If all the males are fished, there will not be enough males to mate with all the females, and the ones that are left will be small so not as able to mate with as many females. The numbers of Row and Mau will decrease quickly. In the Morfach, the larger fish are making more eggs and sperm so can make many more babies. If the large ones are gone, the numbers of Morfach on the reef will decrease quickly. On Ulithi, these fish used to be caught in nets or traps, which catch all sizes, which does not cause the same problem.