Wachenfeld et al., 1998:

Diversity, distribution and population status

"The waters of northern Australia support a wide diversity of sea snakes with 31 species recorded from the area of which 48% are endemic. Seventeen species of sea snakes have been reported from the Great Barrier Reef World Heritage Area. Some species are found mostly on and around coral reefs whereas others are found over sandy and muddy areas of seabed. Many species are specialist feeders that are restricted to the specific habitats used by their prey. Research suggests that some species use shallow, inshore habitats as nursery grounds.

There have been few studies conducted on sea snakes in the Great Barrier Reef and the status and distribution of populations is unknown. Nevertheless, sea snakes are known to be relatively long-lived animals with low reproductive outputs. This means that as the number of breeding adults in a population declines, the number of young replenishing the population may also decline rapidly. This also means that populations may take a long time to recover once depleted. Collectively, these traits make sea snakes more vulnerable to pressures than shorter-lived species that produce plenty of young."

Pressures

"The limited information available suggests that the main pressure on sea snakes is incidental catch in trawl nets (bycatch). Disturbance from vessel noise and boat strike have also been listed as pressures on sea snakes in Northern Australia but no scientific studies have been conducted on the effects of these activities."

Pressure: incidental catch

"In the Great Barrier Reef, sea snakes that roam over the seabed away from coral reefs may be accidentally caught in trawl nets. However, most of the research about sea snake bycatch in trawl nets has been conducted in the Northern Prawn Fishery that operates in the Gulf of Carpentaria and Northern Australia. These studies have shown that sea snake bycatch varies between different areas, depth ranges and seasons and that some species are more susceptible to capture than others. The survival rate of captured sea snakes also differs between species, but survival is also dependent on the duration of the trawl and the weight of the catch contained in the net.

Research has also shown that female sea snakes are caught more often than males, and that mature snakes are caught more often than juveniles. Overall, it is thought that up to 33% of sea snakes caught in trawl nets die either by drowning or from injuries sustained during capture. The species most at risk from trawling are those that are most easily captured, are rare, and/or have lower capacities to recover. Trawling in areas where sea snakes aggregate can significantly increase the incidental catch of these animals and could have significant impacts on sea snake populations."

Pressure: habitat degradation

"Pressures that affect sea snake habitats are likely to indirectly affect the sea snake populations that rely on these habitats. Coral reefs, seagrass meadows and benthic habitats may be affected by large-scale pressures such as declining water quality and climate change, as well as localised pressures such as anchor damage and  dredging. In inter-reefal and lagoonal areas, repeated bottom trawling may remove up to 90% of the seabed biomass, effectively removing benthic habitats that may be important sources of food or shelter for sea snakes."

Response

"There are currently few management responses specifically directed at sea snake conservation in the Great Barrier Reef. The lack of information on sea snake populations presents a challenge to Reef managers in identifying the most appropriate management response. Nevertheless, given the vulnerability of some sea snake species due to their life history traits and the potential for sea snakes to be caught in trawl nets, the most appropriate management response is to minimise the pressure from known human activities while initiating research programs to inform a long term management approach. As with turtles, the introduction of appropriate bycatch reduction devices on trawl nets should greatly reduce the human pressures on sea snake populations. More information on the abundance, population dynamics, distribution and impacts of human activities is required to comprehensively assess the pressure, risks and management priorities for sea snakes on the Great Barrier Reef."

Summary

"The status of sea snakes in the Great Barrier Reef Marine Park is virtually unknown, although trawling is a known pressure. In the absence of status and trend information, management requirements are uncertain. The only course of action is to use the precautionary approach in the short term, minimise the pressure from trawling, and instigate a research program to fill the information void."

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Citation and/or URL

Wachenfeld,  D.R., Oliver, J.K., and Morrissey, J.I. [Eds.} (1999). State of the Great Barrier Reef World Heritage Area 1998.  Great Barrier Reef Marine Park Authority. 

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Spatial Coverage

Great Barrier Reef World Heritage Area

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Temporal Coverage

30 years

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Update Frequency

Not applicable 

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Other Information

None