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 The inshore trawl fishery is a relatively small and declining component of the Tasmanian fishery. However, there is a common perception that perceived declines in certain scale fish fisheries lay totally with the trawl fishing sector and that any large fishing vessel is a 'trawler'. This case study seeks to address this misconception. Demersal (bottom) trawling can have a substantial impact on natural marine systems. The severity of the effects of trawling in a particular place are largely related to the type of gear used (some types cause less bottom damage), the frequency of trawl passes over a particular location and the sensitivity of the flora and fauna to trawl damage. The intensity of trawling in a particular location is proposed as a measure of pressure from trawling in those fishing grounds (Ward et. al. 1998) The Tasmanian inshore trawl fishery (within State waters, generally within three nautical miles of the coast) has existed as a small segment of the fishing industry since the 1930s. Relatively few vessels participate at any one time (historically less than 15, only two to four in recent years) and available fishing grounds can only support limited effort. Much of the seabed adjacent to Tasmania is unsuitable for trawling due to rocky outcrops and heavy shale bottom, or is closed to the fishery for conservation purposes (Lyle 1994). Two fishing methods are used in the inshore trawl fishery: otter board trawling and Danish seining. Otter board trawling involves a vessel towing a large funnel shaped net by means of wires. These wires (warps) lead from the stern of the vessel and are attached to otter boards (doors) which spread open the mouth of the net when towed through the water. The net may be towed for several hours with the boards and warps herding fish into the net. Danish seining involves a vessel shooting away a buoyed length of rope (approximately 1,000 m) followed by a funnel shaped net and a further similar length of rope. This operation is carried out while the vessel is steaming in a precise pattern returning to the original buoy from which the rope is retrieved and hauling of both ropes commences. The movement of the ropes over the sea bed herds the fish towards the net and the entire operation takes about one hour to complete (Lyle 1994). Danish seining is generally acknowledged as having much less detrimental effect on the bottom habitat than otter board trawling. Danish seiners generally target whiting and use nets with small mesh codends that are necessary to retain the whiting. Flathead and flounder are a common by-catch. Otter board trawlers target 'market' fish such as flathead, jackass morwong and warehou and the nets have larger codend mesh sizes designed to retain fish of marketable size (Lyle 1994). The trawl fishery developed rapidly during the 1980s and expanded offshore into deeper water. When the Commonwealth managed South-east fishery (SEF) was defined as a limited entry fishery in 1985, a number of Commonwealth endorsed trawlers had Tasmanian fishing boat licences (TFBL's), permitting access to State waters. Prior to 1991, the Tasmanian inshore trawl fishery operated with minimal management arrangements. Any fisher possessing a TFBL had access to the fishery which resulted in a large amount of latent (potential but unused) effort in the fishery. Since 1988, between two and 14 vessels reported inshore trawl activity in any one year, with a maximum of seven Danish seiners and seven otter trawlers in 1991 (Lyle 1994). Prior to 1988, monthly fishing logbooks did not specify trawling as a specific method, so catch and effort levels could not be determined. The collection of monthly (rather than daily or individual shot) data, inappropriate effort information and poorly defined spatial resolution represented major constraints in the assessment of the fishery. Between 1988 and 1994, inshore trawl catches ranged between 260 and 550 tonne with Danish seine landings generally comprising the greater proportion of the catch. During this period, the three main trawl grounds, i) Storm Bay (42%), ii) the east coast between Schouten Island and the Tasman Peninsula (33%) and iii) around Stanley (15%), accounted for approximately 90% of the catch (Lyle 1994). This percentage is indicative of where most effort was concentrated. In 1992, the Inshore trawl management plan was introduced to prevent unsustainable expansion in fishing capacity, while accommodating fishers already in the fishery. Only fishers who had a history of trawling in State fishing waters qualified for a license. Two categories of non-transferable inshore trawl license were created: limited trawl and general trawl. The Limited trawl licence applied to SEF vessels with a prior history of inshore trawling and restricts trawling in state waters to a defined area of Storm Bay. A general trawl licence applies to fishers who had no involvement in the SEF trawl fishery and allows trawling in all State waters not closed to trawling. Closed trawling areas recognise the potentially destructive nature of some trawling activities and that conflict can exist between trawling and other commercial fishing sectors or recreational fishers. Therefore, trawling is prohibited within one nm of the coastline of Tasmania and is prohibited adjacent to or within certain rivers, estuaries and lagoons. Trawling is prohibited within Andersons Bay, Great Oyster Bay, Mercury Passage, D'Entrecasteaux Channel, Norfolk Bay, Frederick Henry Bay and the Derwent River (however, Danish seine vessels with a substantial history of whiting catches in Frederick Henry Bay and the Derwent are endorsed to use small mesh nets within specified 'whiting' areas in these regions) In 1995, a new logbook was introduced that for the first time provided daily information on catch and effort for the inshore trawl fishery. Catch and effort is recorded in blocks at a 1/4 degree spatial scale. Since this time, catches of the main inshore trawl fishes (flathead, whiting and jackass morwong) have declined sharply, reflecting an overall decline in trawl effort. However, due to confidentiality reasons, this greatly improved catch and effort data can not be reported because fewer than five vessels have been involved in the fishery. Management of the Tasmanian inshore trawl fishery is currently under review. It has been proposed that otter board trawling be prohibited in State waters, as this type of fishing gear no longer reflects responsible fisheries management policy. In the short-term, the small amount of Danish seine fishing for whiting that occurs will remain. Non-transferability of licences ensures that all trawling will gradually be eliminated from Tasmanian State waters. Ray Murphy, DPIWE |
