Andrew G. Wood; Photo Researchers. Inc. 



In the northwestern Hawaiian Islands, pyramid butterfly 

 fish, below, school above a reef. A small bassletfish, 

 right, hugs the reef, looking for food. 



Nikolas Konstantinou: Photo Resource Hawaii 



the satellite data were also ready and 

 showed that phytoplankton production 

 around Hawaii was highest during the first 

 quarter of each year when the Aleutian 

 low was strongest. Mean chlorophyll den- 

 sity estimated from the satellite was about 

 40 percent higher during the first quarter 

 of each year from 1981 to 1983 than dur- 

 ing the same period in the years immedi- 

 ately before 1981 and after 1983. 



From the bottom to the top, all four 

 major levels of the nearshore marine 

 ecosystem in the northwestern Hawaiian 

 Islands reflected the changing atmos- 

 pheric conditions. As the Aleutian low 

 reached its greatest intensity and eastward 

 position in the early 1980s, the westerhes 

 blowing across northwestern Hawaii gath- 

 ered strength. The resultant wind-driven 

 currents and rough seas increased the 

 amount of vertical mixing of ocean wa- 

 ters, so that nutrients were transported 

 from deep waters to the surface, thus in- 

 creasing phytoplankton production. 



Higher phytoplankton densities observed 

 in the early 1980s, translated into more 

 zooplankton, which in turn supports a 

 greater abundance of flying fishes and 

 squid, which are prey for seabirds. Abun- 

 dant plankton could increase the survival 

 of reef fishes and lobsters, which eat 

 plankton during their long larval phase. 

 And expanded populations of reef fishes 

 and lobsters would provide more food for 

 monk seal pups. 



The first quarter of each year seems to 

 be a critical time for many animals, so 

 when the Aleutian low began to wane in 

 the mid-1980s, it would have had an im- 

 mediate effect. As juvenile flying fish and 

 squid declined in number, seabirds would 

 spend more time away from their nests 

 looking for food, leaving their eggs or 

 chicks exposed to the sun. An immediate 

 decline in the survival of lobster larvae 

 would have occurred, but because lobsters 

 trapped by the lobstermen are three to four 

 years old, the decline wouldn't be ob- 



served until the very late 1980s and early 

 1990s. Because monk seal pups will only 

 eat lobsters and reef fishes that are at least 

 several years old, a decline of monk seal 

 pup survival would not have been evident 

 until the late 1980s as well. Thus the time 

 lag between declines beginning in the 

 mid-1980s for seabirds but late 1980s for 

 monk seals and lobsters is explained. 



I went back to the lobster fishermen and 

 told them I had good news and bad news: 

 the good news was that the decUne in lob- 

 ster catches wasn't due to overfishing; the 

 bad news was that, unless the Aleutian low 

 strengthened again, they were stuck with 

 the current low marine productivity and 

 poor lobster catches for a long time. 



While the case of the vanishing lobster 

 appears solved, I've learned from years of 

 experience that ecosystems are compli- 

 cated characters. We should not always 

 count on nature to provide the same har- 

 vest; natural changes in cUmate can work 

 for or against us. D 



58 Natural History 2/94 



