Murray–Darling Basin Authority Native Fish Strategy Strategies to improve post release survival of hatchery-reared threatened fish species Michael Hutchison, Danielle Stewart, Keith Chilcott, Adam Butcher, Angela Henderson
Download 3.02 Mb.
|
- Navigate this page:
- Treatment VIE tag colour
- Predator free cage prior to release (soft release) Standard release Fish predator trained
- Predator naïve
| Figure 8: Habitat characteristics of stocking sites: A. Cotswold Dam
B. Reilly’s Weir pool (during rising flow) C. Caliguel Lagoon D. Storm King Dam (Photos by M. Hutchison) Tagging A total of 24,000 fingerlings of Murray cod and silver perch were ordered from hatcheries for use in the stocking experiments. Unfortunately no hatcheries were able to supply sufficient numbers of Condamine strain freshwater catfish for stocking experiments. Fingerlings were tagged with fluorescent visible implant elastomer (VIE) tags at the base of the anal fin in both species (Figure 9). Past work by Gallagher and Hutchison (2004) and Simpson (unpublished) have demonstrated that the base of the anal fin provides good tag visibility and tag retention in silver perch and Maccullochella spp. VIE tags also appear to have no significant effect on predation rates of fingerlings (Haines & Modde 1996; Malone et al. 1999; Roberts & Kilpatrick 2004; Reeves & Buckmeier 2009; Bouska & Paukert 2010). Tagging was done using two Northwest Marine Technology (NMT) air driven tagging machines. Up to 3000 fish were tagged in a day. Four colours were used to represent the different treatments (Table 2). The numbers of fish from each treatment planned to be stocked at each site are shown in Table 3. Table 2: Release treatment and VIE batch tag colours.
Table 3: Planned number of fish to be stocked by treatment and release method at selected sites in the Murray–Darling Basin
Figure 9: VIE tagged Murray cod. Note green tag at base of anal fin. (Photo M. Hutchison) VIE tag retention trial As it was originally intended to conduct stocking trials with freshwater catfish a VIE tag retention trial was also run with this species. Sixty anaesthetised freshwater catfish with a mean size of 58.98 mm (±7.12 mm) total length were VIE tagged in translucent tissue near the lower jaw (Figure 10) with a NMT hand tagger. The lower jaw appears to be the only suitable location to VIE tag small catfish where the tags can be observed without sacrificing the fish. Other body locations have opaque skin tissue that obscures the tag, even under UV light. After tagging, the catfish were maintained in a 1000 L tank for five months. Catfish were fed a mix of frozen (bloodworm and pieces of prawn) and pellet foods. Tanks were cleaned daily and water changed regularly. 
Figure 10: VIE tagged catfish fingerling. Note red tag near lower jaw. PIT tag retention trial After fish were at large for 12 months and large enough to individually tag, it was planned to use passive integrated transponder (PIT) tags for a mark recapture experiment. As fish could be targeted by anglers in the future and eaten, it was decided to tag these fish in the gut cavity rather than in the dorsal muscle. This would minimise the chance of people accidentally ingesting a PIT tag. To determine if this was a suitable tag location 40 anaesthetised silver perch of a mean size of 172.4 mm (±28.3 mm) FL were tagged with Trovan® PIT tags by inserting the PIT tag needle at a shallow angle into the upper rear gut cavity. Just as the needle penetrated the muscle wall into the gut cavity, the tag was injected. Following tagging the silver perch were maintained in a 7000 L tank for six weeks and fed a diet of commercial pellet and prawns. Water quality was maintained with a biofiltration system. Tagged fish were monitored for post tagging mortalities or complications. After six weeks tag retention was determined by scanning each fish with a Trovan® PIT tag reader. As the mark recapture population estimate experiments were not intended to last for more than a month, six weeks was considered an adequate monitoring period. Directory: sites -> default -> files -> pubs files -> Northern England’s set-jetting locations files -> Nstructions for Acquiring Excess Equipment online, through the 1033 Program files -> Occupational health and safety files -> The Black Panther Party’s Ten Point Program files -> International programs roel profile files -> Fermi Questions a guide for Teachers, Students, and Event Supervisors Lloyd Abrams, Ph. D. DuPont Company, cr&D/ccas experimental Station Wilmington, de 19880 files -> Personal Information Name: Maha Al-Ammari Nationality: Saudi Relationship Status pubs -> Aboriginal Partnerships Action Plan Download 3.02 Mb. Share with your friends:
|