FAQ - Why is it necessary to collect a specimen?
Why collect specimens, why not just visually record the presence of a species? Indeed, why not take a photograph?
For some well known common species of fishes such as the Comb Wrasse, a photographic record, and even a sight record can be very useful. Problems arise however if the validity of the record is ever questioned. A sight record is worth very little because it cannot be validated. A photograph is useful but often doesn't display important characteristics such as the number of gill rakers or any internal character that may be required to confirm the identification of the specimen.
Another major reason for collecting fish specimens rather than just recording observations, is that many species are never seen. They live in a burrow or deep in the rocks or coral. A good example is the Palespotted Podge, Pseudogramma polyacantha (see imgage). This is one of the most common fishes collected in Indo-Pacific coral reef fish surveys. It lives deep inside the coral but is never observed alive by divers. Unless intensive collecting techniques are used only a fraction of the true biodiversity is recorded (Ackerman & Bellwood, 2000).
Dr J. Williams of the Smithsonian Institution stated that:
- on the Navassa Island biodiversity survey (see further reading below), we used visual censusing and underwater video footage, as well as dipnetting, line fishing and rotenone (plant root powder which affects fish) stations.
- Of the five blennioid families (blennies and related fishes) we collected 19 species(and possibly a few more that couldn't be identified in the field), using rotenone. In terms of numbers these were among the most common fishes.
- We searched the same and similar areas visually and could only find two of the 19 species during the visual censuses or on the video tapes. Without collecting the specimens using rotenone, we would have missed 17 of the 19 blennioid species at Navassa, including an undescribed species of Acanthemblemaria (family Chaenopsidae, the pikeblennies, tubeblennies and flagblennies).
- A strict visual census would have missed not only a major chunk of the biodiversity, but much of the biomass as well. These small cryptic fish are the food of the commercially important species.
In his visual census of Vanuatu fishes, D. Williams (1990) recorded 469 species of fishes. These workers recommended that a more complete assessment of the Vanuatu fauna was required using intensive collecting techniques. "Such a study by experienced collectors such as those at the Australian or West Australian Museum is recommended.". The Australian Museum in collaboration with other museums and Vanuatu Fisheries collected fishes in Vanuatu on two trips in 1996 and 1997. These trips verified the comments of Williams. On these trips, fishes from 40 families not recorded in William's visual census were collected. These include many species recorded from Vanuatu for the first time and indeed a number were new species. These data have been supplied to Vanuatu Fisheries who now have a more complete picture of their fish fauna. This information can be used to make conservation and fisheries management decisions.
- Ackerman, J.L. & D.R. Bellwood. 2000. Reef fish assemblages: a re-evaluation using enclosed rotenone stations. Marine Ecology Progress Series 206: 227-237.
- Collette, B.B., Williams, J.T., Thacker, C.E. & M.L. Smith. 2003. Shore fishes of Navassa Island, West Indies: a case study on the need for rotenone sampling in reef fish biodiversity studies. Aqua. 6(3):89-131.
- Paxton, J.R. & M. McGrouther. 1991. Why so many specimens? Muse (Australian Museum News & Events) Aug -Sept. 1991:4, 11, 2 figs.
- Smith-Vaniz, W.F. Jelks, H.L. & L.A. Rocha. 2006. Relevance of cryptic fishes in biodiversity assessments: a case study at Buck Island Reef National Monument, St. Croix. Bulletin of Marine Science. 79(1): 17-48.
- Williams, D.McB. 1990. Shallow-water Reef Fishes. in Done, T.J. & Navin, K.F. (eds) Vanuatu Marine Resources: Australian Institute of Marine Science, Townsville. Pp. 66-76.
Mark McGrouther , Collection Manager, Ichthyology