Project number:
1995-058
Project Status:
Completed
Budget expenditure:
$87,600.00
Principal Investigator:
Tony Koslow
Organisation:
CSIRO Oceans and Atmosphere Hobart
Project start/end date:
29 Dec 1995
-
23 Sep 1998
Contact:
FRDC
1. Assess the impact of trawling on the seamount fauna in the Southern Zone based on photographic transects of fished, lightly fished, and unfished seamounts in the Southern Zone
2. Assess the species composition of the seamount fauna in hte Southern Zone in relation to depth and position on the seamount based on photograqhic transects of seamounts peaking at depths between 600 and 1500m. Limited dredging will be required to obtain samples for species identification
3. Sample the motile fish and invertebrate species in the seamount coraline enviroment with baited traps to assess the role of the environment as a nursery ground for juvenile fish and as a source of prey species for commercially exploited fishes
Final report
ISBN:
0 643 06171 1
Author:
Tony Koslow
Final Report
•
1998-09-07
•
2.82 MB
1995-058-DLD.pdf
In September 1995, the deepwater trawl fishing industry agreed not to trawl in an area of 370 km2 on the continental slope south of Tasmania for three years, as stated in a Memorandum of Understanding between the former Australian Nature Conservation Agency (now Environment Australia) (EA) and the Australian Fisheries Management Authority (AFMA). The purpose of the moratorium was to allow time for CSIRO to conduct scientific investigations and provide Government with sufficient information to assess future management options. The primary objectives of the research were to assess 1) the uniqueness of the benthic seamount fauna in the region, 2) the potential impacts of the deepwater trawl fishery upon it, and 3) the measures required to conserve it.
In January 1997 CSIRO surveyed 14 seamounts in the region, both inside and outside the Interim Protected Area and over a range of depths and degrees of prior commercial trawling
(from unfished to heavily fished). Species richness of the benthic seamount fauna is high in global terms: 262 species of invertebrates and 37 species of fish were recognized from the samples from this single cruise, compared with 598 species reported worldwide from all seamount studies conducted prior to 1987. On seamounts that peaked at depths < 1400 m and that had not been heavily fished, the invertebrate fauna on the slopes was dense and diverse. It was generally dominated by filter feeders, in particular a matrix-forming colonial hard coral, Solenosmilia variabilis, but including a variety of hard and soft (gorgonian and antipatharian) corals, hydroids, sponges and filter-feeding groups of ophiuroids and sea-stars. Many species were associated with S. variabilis, using it either as their point of attachment to the substrate or for shelter. This fauna has elements distinct from the fauna found elsewhere on the continental slope and at least 24-43% of the invertebrate species are new to science. Between 16 and 33% of the invertebrate species are believed to be restricted to the seamount environment. Many of the species appear to have restricted distributions and differ from species found on seamounts around New Zealand.
(from unfished to heavily fished). Species richness of the benthic seamount fauna is high in global terms: 262 species of invertebrates and 37 species of fish were recognized from the samples from this single cruise, compared with 598 species reported worldwide from all seamount studies conducted prior to 1987. On seamounts that peaked at depths < 1400 m and that had not been heavily fished, the invertebrate fauna on the slopes was dense and diverse. It was generally dominated by filter feeders, in particular a matrix-forming colonial hard coral, Solenosmilia variabilis, but including a variety of hard and soft (gorgonian and antipatharian) corals, hydroids, sponges and filter-feeding groups of ophiuroids and sea-stars. Many species were associated with S. variabilis, using it either as their point of attachment to the substrate or for shelter. This fauna has elements distinct from the fauna found elsewhere on the continental slope and at least 24-43% of the invertebrate species are new to science. Between 16 and 33% of the invertebrate species are believed to be restricted to the seamount environment. Many of the species appear to have restricted distributions and differ from species found on seamounts around New Zealand.
Trawl operations appear to have significantly impacted the most heavily fished seamounts, such as Main Pedra and Sister, where the reef aggregate has been mostly removed from the slopes or turned to rubble. The benthic biomass from heavily fished seamounts was 83% less than from lightly fished or unfished seamounts and the number of species per sample was 59% less. No significant differences in benthic biomass, species richness or species composition were found between lightly fished seamounts outside the reserve and seamounts in the reserve that peaked at depths < 1400 m.
In summary, seamounts in the region contain a diverse fauna characterized by a high proportion of species endemic to local seamounts, although the full extent of their distribution cannot be assessed without further exploration. The fauna is highly vulnerable to trawling and is likely to have limited resilience, as its slow growth and low natural mortality are adapted to an environment with little natural disturbance.
The report therefore recommends that the present Interim Protected Area be fully protected in a Marine Protected Area (MPA) that is permanently closed to all fishing or other activity that may potentially disturb the seamount benthic fauna and associated ecosystem. The seamount fauna within the Interim Protected Area meets the biogeographic, ecological, scientific and naturalness criteria adopted by the International Maritime Organisation for designation of protected areas (Kelleher and Kenchington (IUCN), 1992). The proportion of seamount habitat within the Interim Protected Area is consistent with the proportion of a habitat generally recommended for inclusion in protected areas (between 10 and 20%).
