3 SPC Beche-de-mer Information Bulletin #33 – May 2013 Introduction Sometimes, weight data for sea cucumbers are available for only one stage of processing, whether this be the pre-processing stage (fresh weight), an intermediate processing stage or, more commonly, the fully processed dried product (beche-de-mer). Conversion ratios allow weight data to be com- pared using a common unit for analysis. If accu- rate conversion rates are available for a particular species, the processed weight can be used in order to estimate the weight (and numbers, if average weights are available) of fresh sea cucumbers that were processed. Some previous studies have determined the aver- age change in weight from whole, unprocessed sea cucumbers to dried beche-de-mer for several common tropical species (Conand 1990; Skewes et al. 2004; Purcell et al. 2009; Lavitra et al. 2009). However, there are still knowledge gaps for some commercial species, several of which have been addressed in this study. In addition to differences between species, the conversion rates for the same species may vary, depending on country/location/environment, and also on the processing standards and methods used. To date, no sea cucumber weight conversion Change in weight of sea cucumbers during processing: Ten common commercial species in Tonga Poasi Ngaluafe 1* and Jessica Lee 2 Abstract Accurately estimating the weight of live sea cucumber from the weight of dried beche-de-mer is important for national fisheries data, for standardising data collected from surveys or export records, and for inform- ing management decisions and regulating fisheries quotas. Different sea cucumber species lose different proportions of their body weight through processing, so conversion ratios are best calculated on a species- by-species basis. This study measured the proportional change in weight of ten sea cucumber species in Tonga over the various stages of processing. The aim of the study was to fill knowledge gaps by providing conversion ratios for species for which no relevant data exist, such as Actinopyga lecanora, Bohadschia argus, B. similis, B. vitiensis and Holothuria coluber. For other species studied, the conversion ratios were compared with the ratios calculated in previous studies, with this study generally producing higher conversion ratios (i.e. less weight lost through processing). We discuss the possible reasons for this discrepancy, the implica- tions for fisheries management in Tonga, and the need for further studies. studies have been carried out in Tonga. Comparing the ratios obtained in this study to those reported in previous studies will help the Tongan Fisheries Department to decide whether the ratios currently being used for catch calculations are appropriate to Tonga. Methods The methods followed were based on the methods used by Purcell et al. (2009), with some variations. Length conversion information was not considered in this study, as it is not as relevant as weight con- version information for commercial export calcula- tions in Tonga. The study was conducted in Uiha on the island of Felemea, in the Ha’apai group of islands in Tonga. Sea cucumbers were collected by local fishers and brought to shore in tubs. A sample size of twenty- five individuals was weighed for each species, with the exception of Thelenota ananas (prickly redfish), with only 14 individuals recorded, and Actinopyga sp. (affinity flammea) with only two individuals recorded. The sea cucumbers were allowed to drain for one minute before being weighed to the nearest 10 g in a plastic bag on a digital hanging scale. They were 1 Head of Aquaculture Research and Development, Fisheries Division, Tonga 2 Australian Volunteer Development Programme, Aquaculture Research and Development, Fisheries Division, Tonga * Email: poasi66@hotmail.com