Abstract
A study was carried out on the size distribution, length-weight relationship and condition factor of a deep-water population of the commercially important tropical sea cucumber Holothuria scabra in Zanzibar, Tanzania. Samples were collected from fishers and supplementary information gathered. The deep water (15-20 m) population of H. scabra is dominated by large sized individuals that have already attained maturity. There was no significant difference in size between male and female individuals (p>0.05). The sex ratio in this population significantly differed from 1:1 in favour of male individuals (p=0.01). The results showed significant correlation between length and weight for male, female, indeterminate individuals, and pooled data, with r values of 0.681, 0.794, 0.821 and 0.680, respectively. Moreover, the b-value for male, female, indeterminate individuals and pooled data was 1.288, 1.439, 1.686 and 1.407 respectively, which revealed that individuals of deep-water H. scabra exhibit negative allometric growth. The mean condition factor (K) value when all data were pooled together was 4.213±0.106 indicating that individuals were in good condition and came from a healthy environment. This study fills a key information gap that is relevant to the management of the H. scabra fishery in the country.
Highlights
Sea cucumbers constitute an important part of marine fisheries in Tanzania (Semesi et al, 1998) and have provided a source of income to individual collectors as well as revenue at a national level through export (Eriksson et al, 2010)
It can be concluded that the deep-water population of H. scabra on the west coast of Unguja Island, Zanzibar mainly consists of large sized mature individuals
Like other sea cucumber species, H. scabra from this study shows negative allometric growth, i.e. length increment is faster than weight increment
Summary
Sea cucumbers constitute an important part of marine fisheries in Tanzania (Semesi et al, 1998) and have provided a source of income to individual collectors as well as revenue at a national level through export (Eriksson et al, 2010). As in other producing countries across the region, the resource has already dwindled in Tanzania as evidenced by catch reduction, dominance of small size individuals ( Jiddawi, 1997; Mgaya and Mmbaga, 2007; Mmbaga, 2013) and a decrease in the number of exporters (Marshall et al, 2001). This represents a significant threat to the sea cucumber population, ecosystem (Uthicke, 1999) as well as the safety of fishers (Eriksson et al, 2010)
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