Profile of the illegal abalone (<i>Haliotis midae</i>) fishery in the Eastern Cape, South Africa: organised pillage and management failure

Since 1997 the Eastern Cape of South Africa has become a major source of supply for the illicit abalone trade as illegal fishers have located a substantial abalone (Haliotis midae) resource. We determined illegal fishing effort and yield in the Port Elizabeth-based abalone fishery, and used biological indices to determine the impact of fishing on the abalone stock. The failure of the state to issue fishing rights and conduct effective sea-based compliance, combined with the incentives to fish abalone (high price, low cost, ease of access) created the conditions for a full scale illegal fishery to emerge very rapidly. By 2005, the scale of the fishery was remarkable: a fleet of 30 purpose built vessels existed, harvesting 1000–2000 tons of abalone with an export value of 35–70 million USD per year. The uncontrolled fishing effort had a dramatic effect on the stock: the average size of abalone decreased significantly, densities declined in the sampling areas, but recruitment of young abalone was still observed at the heavily fished Cape Recife site. It is concluded that the illegal fishing operations and the resultant ecological effects on the abalone resource, reflect deficiencies in South Africa's current abalone fisheries management and compliance paradigm

The effect of low-level kelp supplementation on digestive enzyme activity levels in cultured abalone Haliotis midae fed formulated feeds

Previous studies have found that macroalgal inclusion in formulated diets for cultured abalone improves feed utilisation, and it was suggested that seaweed-associated bacteria supply enzymes that aid in the animal’s digestion. In the present study, we hypothesised that kelp supplementation in formulated feed affects the profile of digestive enzymes in farmed Haliotis midae. Commercially reared sub-adult abalone fed a kelp-supplemented (Ecklonia maxima; 0.88% dry weight) or kelp-free control feed were collected for analysis of the amylase, alginate lyase, laminarinase, fucoidanase and protease activities in the gut. Levels of polysaccharidase and protease activity did not significantly differ between the diet treatments. However, enzyme-activity levels were more variable in abalone fed the kelp-free diet as compared with those fed the kelp-supplemented diet (coefficients of variation: 73%, 48.3–60.2% and 31.9% [control diet] versus 42.7%, 13.6–33.8% and 14.6% [KS diet] for amylase, macroalgal polysaccharidases and acid protease activity, respectively). We suggest that the presence of dietary kelp modulates the abalone’s gut bacteria and their nutrient exchange. Proteomic identification of proteins in abalone gut sections showed that exogenous enzymes associated with the gut microbiome aid in bacterial utilisation of digested molecules, whereas abalone endogenous enzymes degrade the macronutrients in formulated feeds.Keywords: digestion, exogenous enzymes, gastropod, mariculture, proteins, proteomic identification, seaweed, South African abalon