40 www.themercury.com.au WEDNESDAY, JUNE 30, 2010

FISH TALES

HOBART’S UNDERWATER WORLD

n our daily lives the Derwent estuary Ready to go fi shing? appears as a stretch of water dividing The Derwent estuary offers excellent fi shing IHobart into eastern and western shores, and whatever the weather there is often a but under the surface is a fascinating sheltered bay or cove where you can cast a world of fi sh. line. The most commonly targeted species About 150 different kinds of fi sh live in include fl athead, bream, trout, Australian the the Derwent estuary. They come in all salmon and cod. For more information about shapes and sizes, ranging from sharks, to what to catch and where see the Department the often-fi shed fl athead, to tiny near- of Primary Industries, Parks, Water and the transparent whitebait. Environment website www.dpipwe.tas.gov.au/inter.nsf/WebPages/ Where do they live? ALIR-4YB6HE?open#DerwentEstuary Fish can be divided into three types depending on where they are found. It is recommended to refer to the Recreational Sea Fishing Guide and the ■ Pelagic fi sh live in the water column. In Tasmanian Inland Recreational Fishing Code the Derwent, these typically include: before going fi shing. These are available from eastern Australian salmon, silver trevally, Service outlets and most bait and barracouta, jack mackerel, silver dory, Black bream (Acanthopagrus butcheri) – NSW Department of Primary Industries. tackle shops, and can also be downloaded school shark, gummy shark and white- from www.fi shing.tas.gov.au or www.ifs.tas. spotted dogfi sh. gov.au respectively. Fish-measuring rulers are once supported a important whitebait fi shery, also available from these outlets. ■ Demersal fi sh live on or near the sea-fl oor. but commercial fi shing was suspended after In the Derwent, most bottom-dwelling fi sh stocks plummeted in the 1950s, leading Safe to eat? fi sh live over soft, muddy sediments and to the closure of the fi shery in 1974. Numbers You can eat some types of fi sh from the include: sand fl athead, school whiting, sea have slowly increased to suffi cient levels for a Derwent, but within limits because of mullet, smooth toadfi sh, elephant fi sh, limited recreational season. historical heavy metal contamination. fl ounder and skates. The Derwent Estuary Program released Black bream an updated brochure entitled Should I eat ■ Reef fi sh are associated with shallow rocky Black bream are popular with anglers for shellfi sh and fi sh from the Derwent? in 2009 reefs, particularly in the lower estuary. their feisty nature, and the Derwent estuary is which included the latest health advice These include: bastard trumpeter, banded nationally renowned for trophy-sized bream. from Tasmania’s Director of Public Health. morwong, Shaw’s cowfi sh, draughtboard JonahJ h YiYick k ffrom ththe TTasmanian i AAquaculture lt and d A recent study at the Tasmanian Aquaculture The brochure emphasises the value of fi sh shark, red cod, wrasse and leatherjacket, Fisheries Institute helps tag and release a 6-gill shark and Fisheries Institute (University of as a healthy food choice and provides the seahorses and pipehorses. in the Derwent estuary. Photo: A. Barnett, Tasmanian Tasmania) found the majority of black bream following advice: Aquaculture and Fisheries Institute in the Derwent are relatively old, ranging Fun Fish Facts – did you know? from 13 to 28 years in age, and that there ■ Do not eat any oysters, mussels or bream in the Derwent, particularly in Ralphs Bay, have been very few breeding events in recent taken from the Derwent estuary between where large numbers of school shark pups years. Black bream caught in the Derwent New Norfolk and the Iron Pot Light were recorded during the 1940s and 50s. should be released, and should not be eaten (including Ralphs Bay). The decline may be related to due to high levels of mercury. losses or possible overfi shing of the adult ■ Pregnant women and young children breeding stock. Nevertheless, Ralphs Bay is should limit consumption of fl athead and still an important region for juvenile school all other Derwent-caught fi sh to no more shark, typically of one to two years in age. than one meal per week, and avoid eating The Derwent is a Shark Refuge Area and other fi sh in the same week. the taking of sharks, skates and rays is prohibited. ■ Other adults should limit their consumption of fl athead and other Derwent-caught fi sh to no more than two meals per week.

The brochure can be downloaded from Eel (Anguilla australis) Photo: Inland Fisheries Service www.derwentestuary.org.au Eels The Derwent Estuary Program The Derwent catchment has one of the The Derwent Estuary Program (DEP) is a largest eel populations in . Adult eels regional partnership between the Tasmanian migrate over 3000km from fresh water to the Government, local governments, industry and sea in order to spawn after which it is believed Spotted handfi sh (Brachionichthys hirsutus) the community to restore and promote the they die. Where they spawn is uncertain but is estuary. The DEP was established in 1999 and believed to be in the South Coral Sea off the Spotted handfi sh has been nationally recognised for excellence coast of northern . That’s a long The endangered spotted handfi sh is a small, in reducing water pollution, conserving swim! After the eggs hatch, the eel larvae are unusual fi sh that is slow-moving and prefers habitats and species, monitoring river health carried south by the East Australian Current Whitebait. Photo: Inland Fisheries Service to “walk” on its fi ns rather than swim. Their and promoting greater use and enjoyment of until they reach the continental shelf. At side fi ns are limb-like and resemble a human the foreshore. this stage the tiny, transparent eels are are Whitebait hand – hence their common name. Prior to known as glass eels. These return to the river The wetlands of the upper Derwent estuary the mid 1980s, it was common throughout their parents left to spawn. Once in estuarine provide critical breeding and nursery habitat the lower Derwent estuary and adjoining waters the glass eels quickly develop into for the group of small semi-transparent bays, but then suffered a serious decline in fully pigmented elvers as they adjust to fresh fi sh known as whitebait – which are made distribution and abundance - thought to be water, and then make their way upstream. up of six different fi sh species that migrate related to the invasion of the northern Pacifi c upstream each spring to spawn and take seastar, combined with poor water quality Sharks shelter in estuarine wetlands and mudfl ats. and habitat degradation. Only a handful of More than 10 species of sharks are found in One whitebait species is the endemic Lovettia populations are now found at sites in the the Derwent, and the estuary is a nursery sealii, which is known to have a life cycle of lower Derwent estuary, but numbers appear area for several commercially important just one year. Whitebait runs are a key driver to be stable. For further details go to species, such as gummy and school shark. for the annual sea-trout runs. They are preyed www.environment.gov.au/biodiversity/ School shark recruitment has declined on by predatory fi sh and eels. The Derwent threatened/publications/tas2002.html

Also supported by the Tasmanian Government, Brighton, Clarence, Glenorchy, , Kingborough and Download previous activity pages from: www.mercurynie.com.au Derwent Valley councils, Southern Water, Norske Skog Boyer, Nyrstar Hobart Smelter, Tasmanian Ports Corporation and Hydro Tasmania.