The impact of emigration on population estimates of deep-sea red crab Chaceon maritae off Namibia

Underwater photography and tag-recapture methods have previously been found to be the most accurate means of assessing the size of the population of Chaceon maritae off southern Africa. However, recent population estimates made by the tag-recapture method appear to be too high. Sources of bias in the estimate that led to violations of assumptions of the Petersen method were investigated. Females migrate into Angola and tend to travel farther than males. Population estimates that used information for males only or that accounted for emigration to Angolan waters are therefore too high. Another source of bias included under-reporting of tag recaptures in 1993.Keywords: emigration, population estimate, red crab, tag-recapture African Journal of Marine Science 2001, 23: 61–6