Benzie and Uthicke, 2003:

"Recent developments of the fishery on the Great Barrier Reef have shown that the level of 500 tonne was actually never fished, and catches of black teatfish drastically declined until the closure of its fishery in 1999."

AND

"A comparison between fished (“blue”) and un-fished ("green") reefs in the main fishing area between Townsville and Princess Charlotte Bay indicated that fishing has reduced density and biomass by at least 75 per cent on fished reefs. Black teatfish stocks on over-fished reefs had not recovered two years after closure of the fishery, while the stocks on reefs previously protected from fishing remained at high densities."

AND

"Given the significantly lower densities of black teatfish on open compared to closed reefs it appears that bêche-de-mer fishing on the Great Barrier Reef has led to a reduction in Holothuria nobilis densities of at least 75 per cent on recently fished reefs. The densities of the fished reefs were all similar (around 5 ind. ha^-1)."

AND

"The surveys conducted were mainly designed for black teatfish, H. nobilis, in that they concentrated on the reef flat area. H. nobilis was shown to be a mid to outer shelf species with it's main abundance at the northern half of the Great Barrier Reef. However, some reefs in the southern areas had high abundances (Whitsunday area and Pompey region). This species was the only high value bêche-de-mer species common in shallow water habitats in the Great Barrier Reef."

AND

"In contrast to most other species studied on the Great Barrier Reef, H. nobilis spawns in winter in New Caledonia (Conand 1993) and, as we have shown in the present study, on the Great Barrier Reef."

AND

"Data obtained here can also be used to assess the mobility of individuals. As expected, no animals from Davies reef matched any on Lizard Island or vice versa, because these locations are hundreds of km apart. On Lizard Island, no individuals migrated between Bird and Palfrey Island (Distance: 2.1km). Animals on the Palfrey Island reef flat were released in two locations only 80 to 90m apart. During the whole study period, only three individuals (out of 62 matches) were found to have migrated between those two locations."

AND

"Model calculations on black teatfish stocks indicated that the virgin biomass was in the order of 5500 tonne and about 5 million individuals. Some of the simplistic fishery models assume a MSY of virgin biomass multiplied by 0.5 times the natural mortality rates (Gulland 1983). However, estimates of mortality rates of holothurians hardly exist, and the few data available (summarised in Conand 1989c) are rough estimates based on other species, several of which have additional asexual reproduction. Using these data to calculate maximum sustainable yields for holothurian populations can be very erroneous. For example, using a mortality rate of 1.0 as a 'reasonable-estimate' for holothurians in general (Long et al. 1996) would suggest that 50 per cent of the virgin biomass of H. nobilis could be caught annually on the Great Barrier Reef and provide a sustainable yield. Based on our lower confidence limit estimates for the biomass this would correspond to 2000 tonne. However, the maximum annual catch for H. nobilis achieved in the Great Barrier Reef was about 370 tonne (catch data provided by QFS). This represents much less than 10 per cent of the biomass of H. nobilis in the target region. In fact, calculations based on the lower confidence limit show catch rates in most years were below five per cent. Thus, with hindsight, it can now be concluded that an annual catch rate of less than 10 per cent of the virgin stock was sufficient to induce severe over fishing. This does not necessarily suggest that fishery models are not adequate for holothurians, but does indicate that mortality rates are much lower than have been commonly assumed. Indeed, the slow growth rates and lack of recovery of the stocks observed during the present study provide evidence that productivity in these populations is very low, and that both recruitment and natural mortality are low."

AND

"This study is among the first to attempt to estimate recovery rates of holothurian stocks. There were no indications of a recovery two years after closure of the fishery for H. nobilis. Densities on both green reefs (protected from fishing even before the closure of the fishery) and blue reefs since closed to fishing remained relatively stable, with green reefs continuing to have some four to five times the average densities of black teatfish as the reefs recently closed to fishing. Hardly any new recruits were observed in any of the
populations. This may be taken as further evidence that animals may be relatively long-lived, because densities would reduce if mortality was high and recruitment low. Densities of black teatfish on reefs divided into Green and Blue Zones did not change significantly over time either. On two of the Ribbon Reefs, densities were higher in the Green zone, indicating that fishing has previously occurred in the Blue Zone. Because the density differences remain constant, it appears that there is no major migration between the two zones. On two smaller reefs, the difference between the Blue and Green Zone was not distinct, and although densities on the blue reefs showed some fluctuation there was no clear sign of a recovery in population size."

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Citation and/or URL

Benzie, J.A. & Uthicke, S. 2003, Stock size of bêche-de-mer, recruitment patterns and gene flow in black teatfish, and recovery of over-fished black teatfish stocks on the Great Barrier Reef. Fisheries Research and Development Corporation Project Report 1998/133, Australian Institute of Marine Sciences, Townsville, Australia

Spatial Coverage

Whole Great Barrier Reef 

Temporal Coverage

1998 - 2001 

Update Frequency

Not applicable 

Other Information

None