Marine Biology Research Division

Specimens of the sea-skater Halobates (Gerridae) were collected in 63% of net tows taken during a 14-month expedition (October 1981 to December 1982) across the Atlantic and the Pacific Oceans between Plymouth, England and Sydney, Australia.  Seven species were found including all five open-ocean species (H. micans, H. sobrinus, H. splendens, H. sericeus and H. germanus) and two coastal species (H. robustus and H. proavus).  The occurrence and abundance of H. micans in the Atlantic Ocean were positively correlated with seawater temperatures.  There was a remarkable similarity between the distribution and age structure of the Atlantic H. micans population in the present study and that of a 1978 expedition along the same cruise track, indicating a high degree of zoogeographical constancy.  Although different Halobates species do co-occur, limits of distribution of the five Pacific species appeared to be well defined. However, we still do not know what determines the distribution patterns of these surface-dwelling insects.