7.24.2003

Rob's Marine Momment

Let me start off this discussion of fish by talking a little about the word fish. What is the plural of fish? How many fish did you see today? Did you see many fishes or many fish? oooh. Good question. It may not be that logical the answer. The plural of one species of fish is 'fish'. So if you saw a school of tuna then you saw many fish. If you saw a school of tuna, however, with a lot of skip-jack and yellow-fin, then you saw many 'fishes'. Fishes means lots of fish of different species. Got it?

Reef fish life Cycle

For those of you that grew up fishing the lakes of our great country of America, you probably are used to catching bass and catfish - maybe crappie's and bluegills too. Do you know how those fish reproduce? Most of them lay eggs on the bottoms of rocks which hatch and then those small fish hang out in the lakes weeds and eat small aquatic insects, etc. Ok.

Now, look at our Hawaiian Ocean. Do you think our reef fish reproduce int he same way? First of all think of where we are in Hawaii. We are the most isolated land mass on earth ... about 2200 mile from the nearest substantial land (Marquesas Is. to SW). If a fish did what our freshwater fish do, they would never have made it to Hawaii. In fact, most have a unique way of breeding.

Most breed through pelagic spawining. What this means is that when conditions are right (every night in summer / only during a full moon / etc), males and females form big courtship schools. Then a female and male will shoot up into the water column - females releasing eggs, males releasing sperm. They mix and wala - fertilized eggs that will float away from the reef and into the open ocean. There are fewer predators in the open ocean so its a more favorable place for the small fry. There they eat plankton and grow up into small larvae. Currents then bring back these larvae to the reefs.

Drawn by the sound of the reef, most larvae will then actively swim down and 'settle' on the reef. This is called 'recruitment'. Recruitment is good.

Management of Open systems

Again, imagine this - Hanuama bay has a ton of fish, right? Other areas are overfished. Do you think Hanauma bay will get more baby fish back than other places simply because it has more adults that are breeding? ... The answer is maybe yes, maybe no. Its an open system you see. If it were closed then what is produced in eggs is what would come back as babies (lakes are closed systems).

In our situation, the number of recruiting fish is dependent on currents. Thats important for selecting an area for protection. If you have a current that moves along the coast. You don't want to protect the very last section on the current, because then the babies wouldn't be able to replenish the rest of the habitats. Instead they would be swept out to sea and never return. Does that make sense? (by the way, thats probably what happens in Haunama bay).

Well, more on individual fish species later.

Happy swimming.

ROB