Size limits

Size limits are another useful tool in managing aquarium fisheries. The marine ornamental fish trade tends to be highly selective in favour of juveniles due to their distinctive coloration, low transport cost for exporters and optimal size to fit in a home aquarium. However, the young of some popular fish species are easily stressed and hence may suffer high mortality during holding and transport6. Setting minimum size limits such as those encouraged by an Ocean Voice International-Haribon Foundation project in the Philippines118 would help ensure that stock is not unnecessarily wasted224. Maximum size limits are equally important to ensure that sufficient numbers of breeding adults remain on the reef. At the recent Nineteenth Meeting of the Animals Committee (18-21 August 2003) the decision of 'a universal minimum permissible size of 10 cm (height) [...] for all seahorses in international trade, [...] to allow animals to reproduce before being caught' was adopted.

The State of Florida has an exemplary regulation system stipulating minimum and maximum sizes for a number of ornamental fish species. According to the Florida Administrative Code butterflyfishes and several species of angelfishes (grey, French, queen and rock beauty), for example, are subject to both a minimum and a maximum length restriction43. Maximum length limits are also specified for gobies, jawfish and the Spanish hogfish43.

Maximum size restrictions for the collection of coral pieces are important to ensure that mature colonies are not removed from the reef. Such restrictions would be particularly useful for species of coral which tend to develop particularly large colonies. The Indonesian authorities have stipulated maximum size limits of 15 cm and 25 cm for slow-growing species such as Plerogyra and Catalaphyllia and fast-growing species such as Acropora respectively224. Removing primarily small specimens is also likely to reduce damage to the reef habitat structure.

A study of Pocillopora verrucosa in the Philippines showed that maximum sustainable yield could be calculated using information on distribution and abundance as well as growth rate and rates of mortality and recruitment225. The minimum size that should be allowed at harvest was calculated to be 18 cm in height, equivalent to six years old.

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