June 27, 2011

Why does Reef Check California record some species even if they are not on transects?


During our Reef Check California surveys we record 73 species of fish, invertebrates and algae. Most of them are only recorded if we encounter them on one of the transect lines we lay out to estimate their population densities. Some species we also record if we encounter them anywhere on the survey dive; they do not have to be on one of our measured transects.

If we record them and they are not associated with a transect, we cannot determine their population density; so why do we record them nevertheless? This is the case for one fish, two invertebrate and four algae species. The reason for recording them this way is different for the algae and animal species. The fish we record anywhere is the giant sea bass (Stereolepis gigas) and the two invertebrate species are white (Haliotis sorenseni) and black (Haliotis craherodii) abalone. These three species are all listed as endangered species. Therefore, noting the occurrence of these species is critical in order to record the presence of these rare species. Over the six years of data collection we have observed only 12 occurrences of giant sea bass and have not seen any black or white abalone.

The seaweeds we record anywhere are recorded for a different reason- they are not endangered, but rather invasive species. We are recording their presence so that their spread along the coast can be tracked, as is the case for the Sargassum species we record, or so that action can be taken to eradicate them if they should occur at our sites, as for the Undaria and Caulerpa species we record.

All seven species are therefore unique in that even the occurrence of one individual can be of great importance and reporting their presence can lead to significant management action.