| Summary: | 碩士 === 國立中山大學 === 海洋資源學系 === 87 === Cage culture along coastal water is a recently development of aquaculture. A net can be encrusted with fouling organisms. The fouling organisms increase resistance to water flow. The additional weight of fouling on cage bags makes net changing difficult. Biofouling will cause net bag deformation by hindering water flow. The composition and succession of epibionts on the cage and their potential consequences have been studied.
In order to understand the biofouling on the cage net, we conducted a survey on the fouling conditions on the cage net along both the coasts of Liuchiuyu and Zukeng of Taiwan. For fieldwork of cage net, the fouling communities in summer and autumn contained more taxon than in spring and winter (maximum difference was 9 taxa.). The parallel-current face of the cage net is more than that on the counter-current face (max. diff. was 12 taxa.), and more at Liuchiuyu than Zukeng (diff. was 6 taxa.). For two orders, April and September, the experiment-net sets of net with mesh size of 1.5cm2, were deployed in the cage culture ground in Liuchiyu. The results showed that the number of species was greater for submersion in autumn than spring. This suggested a temperature difference for net settlement between these two season. After observing for three months we counted more than 30 species from all experiment-nets. The similarity of fouling organisms and biomass of experiment-nets suggested stabilization. The predominant forms were compound algae and burnacle. The sum weight of both can be 50% or over in total weight. Fouling was mostly composed of algae at 1.5 and 3 m depth. An increase at depth facilitated barnacle settlement on nets. However, during September, the experiment-net sets of net with mesh size of 1.5cm2 and 3 cm2, were deployed in the cage culture ground in Liuchiyu. The results showed that the diversity of fouling organisms was more on the smallest mesh size. The most abundant species on the largest mesh was barnacle.
The net mesh congestion could be evaluated from the area of mesh and diameter of the thread of net. Statistical analyses using the linear regression gave the biomass between these two evaluation. The correlation is positive for mesh area and wet weight. The correlation of thread diameter and wet weight is negative. The best relation is between thread diameter and wet weight (coefficient of determination is 0.88). In the future, when fouling necessitates appropriate cage management, we suggest the diameter of thread be an important consideration.
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