Uthicke., 2004:

History of holothurian fishing on the Great Barrier Reef

"Holothurian fishing has a long tradition in Australia and provided the first cultural contact of Aboriginal and Islander communities with non-Australians. These were Macassan fishermen and traders who visited this country centuries before European settlement. Matthew Flinders, one of the early explorers of Australian reported in his “Voyage to Terra Australis:”

"The object of their [the Macassans] expedition was a certain marine animal, called trepang. Of this they gave me two specimens; and it proved to be the beche-de-mer, or sea cucumber which we had first seen on the reefs of the East Coast, and had afterwards hauled on shore so plentifully with the seine, especially in Caledon Bay. They get the trepang by diving, in from 6 to 8 fathoms water; and where it is abundant, a man will bring up eight or ten at a time."

This Macassan fishery in the Northern Territories and West Australia was analysed in detail in a book by MacKnight (1976). The first fishery by Europeans occurred early in the 19th century and was based on the GBR and the Torres Strait, in conjunction with trochus and pear shell exploitation. A first beche-de-mer station was reported in 1804 on Lady Elliott Island, but the operation did not last very long (Sumner, 1981). Further development of the fishery occurred about 40 years later, around 1850, when stations were opened at Green Island (near Cairns), Fitzroy Island and the Frankland Islands (Sumner, 1981). During that period, most fishermen made the long journey from Sydney and played an important role in exploring the tropical east coast of Australia (see reports in Idriess, 1957). The fishery showed the first signs of overfishing in the 1890s (Sumner, 1981). At that time, stocks declined in areas close to the shore and larger boats had to be used to access reefs further off shore.

The author estimated historical catch data for beche-de-mer on the east coast of Australia (Figure 1) with data given in Saville-Kent (1893), Sumner (1981) and Anon (1946). To do this, several assumptions and conversions had to be made (see explanation in figure legend) thus data presented can only be taken as rough estimates. However, it appears that the total volume of previous fisheries was larger than values taken in the current fishery. This may be partly explained by the fact that it is not possible to discern where holothurians were actually fished, because historic data were based on export data from Queensland. These data may therefore include animals fished in the Torres Strait, Coral Sea reefs, Papua New Guinea and the Solomon Islands. This lack of information makes it difficult to put exact figures on boom and bust cycles, but it is clear that the previous cycle ended about the time World War II began, as was also reported by Harriott (1985). It is unclear if this was caused by a single factor such as stock reductions, political or economic reasons, or a combination of factors. The cycles may also be blurred by shifts in species caught, but it appears that most of the catch on the Great Barrier Reef (GBR) at that time was black teatfish (Saville-Kent, 1893), whereas the fishery in the Torres Strait and the Northern Territory was mainly based on sandfish (Holothuria scabra).

 

Figure 1. Historic catch data (in tonnes gutted weight) for holothurians on the Great Barrier Reef and adjacent areas. Early export data were converted from dry-weight (beche-de-mer product) using a conversion factor of 7.6 (combining data for Holothuria nobilis from FAO, 1989; Benzie and Uthicke, 2003). For most years from 1901 to 1940, only the value of the export is reported. These values were converted to weight by assuming an average value of 4.4 Australian Pound per cwt (= 50.8 kg). This figure is the average for the period between 1925 and 1940, derived from Australian export data. Values for the period between 1987 and 2003 are actual catch data obtained from Queensland Fisheries Service.

All commercial holothurians are sediment feeders and consume vast amounts of sediments. Massin (1982a) and Birkeland (1988) suggested that the main functions of holothurians on coral reefs are bioturbation of sediments and the recycling of organic matter. Indeed, it has been shown that populations of two species can move the equivalent of the upper 5 mm of sand in their habitat once a year (Uthicke, 1999). This bioturbation is potentially important for the aeration and cleaning of the sediments and may extend the oxidized layer of these.

The main food sources of holothurians are bacteria, microalgae and dead organic matter (Yingst, 1976; Massin, 1982b; Moriarty, 1982). When holothurians are kept in densities above natural levels, they can reduce algal biomass (Moriarty, 1982; Uthicke, 1999). However, when natural densities were used in experiments, it was demonstrated that benthic microalgae on coral reefs have higher production in the presence of these animals (Uthicke and Klumpp, 1997, 1998; Uthicke, 2001b). The microalgae appear to benefit from enhanced nutrient levels resulting from the excretion of holothurians (Uthicke, 2001a). Since the production by microalgae on sands is an important component of the total production on coral reefs, it can be inferred that removal of holothurians can have negative effects on the total production."

Large-scale holothurian surveys on the GBR

"Initial Surveys

Surveys on over 60 reefs along the entire (spanning 10 degrees of latitude) Great Barrier Reef (GBR) conducted in 1998/99 indicated that stocks of the black teatfish were generally lower in the southern part of the GBR (Figure 3). The zoning of the Great Barrier Reef Marine Park allowed a comparison between reefs that were fished and reefs protected from fishing (Green Reefs or No-Take Zones). Since the southern sections of the GBR were not fished, there is no difference in densities on open and protected reefs. In the northern two sectors, which represent the main fished area north of Townsville (ca. 12 °S to 19 °S) densities are distinctly higher on reefs which are No-Take Zones (Figure 3). A more detailed analysis showed that densities on each of the protected reefs are higher than on open reefs and this difference is highly significant (Figure 4, updated from Uthicke and Benzie, 2000, two additional reefs added from Uthicke and Byrne, unpublished data). On average, fishing has reduced the densities on the fished reefs by about 75 per cent, roughly from densities of 21 individuals per hectare down to 5 individuals. It cannot be concluded with certainty that densities found on No-Take reefs are natural densities, still somewhat reduced from previous fishing cycles (see above), or suffer from reduced larval recruitment due to fishing on other reefs.

Re-surveys after Fishery closure

Nineteen reefs were re-surveyed in the formerly fished area, one and two years after the closure of the fishery, to determine if stocks recovered in that time. During this period, densities on No-Take reefs remained at a high level, one year (2000) and two years (2001) after the fishery closure (Table 1). No recovery was detected on the reefs previously
fished. Densities on these 14 reefs remained on a level substantially below those on the No-Take Zones (Table 1). Although densities on previously fished reefs slightly increased, this increase was not statistically significant (Uthicke et al., in press). The fact that densities do not increase significantly indicates that little recruitment takes place."

 

 

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Citation and/or URL

Uthicke, S., 2004, 'Overfishing of Holothurians: lessons from the Great Barrier Reef'. In 'Advances in sea cucumber aquaculture and management', Lovatelli, A. (comp./ed.); Conand, C.; Purcell, S.; Uthicke, S.; Hamel, J.-F.; Mercier, A. (eds.), FAO Fisheries Technical Paper 463: 163-171. FAO Rome.

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Spatial Coverage

Whole GBR

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Temporal Coverage

Historic 1870 to 2001

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Update Frequency

Not applicable 

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Other Information