Freshwater fish communities and the Hauraki Gulf Paul Franklin National Institute of Water & Atmospheric Research, New Zealand Outline • Introduction to NZ’s freshwater fish • Freshwater fish of the Hauraki Gulf catchments • Why is the Hauraki Gulf important for freshwater fish? – The role of diadromy – Estuaries • Priorities & knowledge gaps Introduction to NZ’s freshwater fish • 53 native freshwater fish species – Endemic: 87% – Threatened: 42%1 – At risk: 36%1 • Important cultural & recreational fisheries – Whitebait, eels, lamprey, flounder • Commercial eel fishery • 20 introduced species 1Goodman et al (2014) Conservation status of NZ freshwater fish 2013. DOC: Wellington. Freshwater fish of the Hauraki Gulf catchments Native Exotic • • • • • • 10 species 20 species 17 migratory 3 non-migratory 2 Nationally Vulnerable 9 At Risk – – – – – – – – – Brown & rainbow trout Perch Rudd Tench Catfish Koi carp Mosquito fish Grass carp Goldfish Freshwater fish of the Hauraki Gulf catchments Inanga Banded kokopu Freshwater fish of the Hauraki Gulf catchments Giant kokopu (red), shortjaw kokopu (blue) & koaro (green) Common smelt Freshwater fish of the Hauraki Gulf catchments Common bully Redfin bully Freshwater fish of the Hauraki Gulf catchments Bluegill bully Giant bully Freshwater fish of the Hauraki Gulf catchments Shortfin eel Longfin eel Freshwater fish of the Hauraki Gulf catchments Torrentfish Estuarine triplefin (red), yellow-eyed mullet (blue) & grey mullet (green) Why is the Hauraki Gulf important for freshwater fish? • Majority of native species are diadromous – Require access to both marine & freshwater to complete their life-cycle – Panmictic populations: random mixing in the breeding population – Source v sink population dynamics • Estuaries: – Important staging area for fish to transition between salt & freshwater – Critical habitat for some species The role of diadromy • Amphidromous: Migrate between freshwater & sea, but not for spawning e.g. whitebait & bullies • Catadromous: Migrate from freshwater to sea to spawn e.g. eels • Anadromous: Migrate from sea to freshwater to spawn e.g. lamprey Amphidromous life-cycle Approximate timing of marine larval phase in amphidromous fish Species Inanga Banded kokopu Giant kokopu Koaro Shortjaw kokopu Common bully Redfin bully Bluegill bully Giant bully Torrentfish Common smelt J F M A M J J A S O N D Catadromous life-cycle - Eels • Spawn at sea (near Tonga/Fiji we think!) • Larvae drift back on ocean currents • Arrive in estuaries as glass eels (Jul-Nov) • May stay for some time in estuary • Migrate into freshwater as elvers (Nov-Mar) • Rear to adulthood in freshwater (& estuaries) Source: www.teara.govt.nz Anadromous life-cycle - Lampreys Rod Morris SPAWNING Larvae (Ammocoetes) Reproductive adult 3-4 yrs 1-1.5 yrs Freshwater Ocean Miniature adult (Macropthalmia) Pre-reproductive adult Feeding adult (feeds parasitically upon other fish) 3-4 yrs The role of estuaries • Resident species – Estuarine triplefin, mullet, flounder – Eels, smelt, giant bully • Critical habitat – Inanga spawning – Transitional staging area • Fisheries – Whitebait, mullet, flounder, eels The role of estuaries • Inanga spawning habitat – Spawning occurs in estuaries March-June – Eggs laid at spring high tide in riparian vegetation – Eggs develop out of water – Larvae hatch next spring tide • Currently no known spawning sites! – Auckland Council have project to try & locate some – WRC failed to locate any in Waihou in recent survey The role of estuaries • Staging area for eels – Glass eels need to transition from salt to freshwater – Progressive transition thought to be important for shift to active upstream migration – Selective tidal stream transport – Probably similar transitional needs for downstream migrating adult eels Source: Sustainable Eel Group Priorities & knowledge gaps • Little known of the marine phase of diadromous freshwater fish species • Use & role of estuarine habitats by freshwater fish species poorly studied • However… Priorities & knowledge gaps • Modification of estuarine/tidal zones will impact freshwater fish – Loss of connectivity: tide gates, stop banks etc – Altered water quality – Sedimentation • Alteration of marine environment will also impact freshwater fish – Larval survival & transport – Food supply & growth A. Offshore islands • Relatively pristine • SJK, Bluegills D. Hunua catchments • Wairoa & Whitford • AC high value E. North shore • BK source populations? • GK populations around Orewa F. Northern • Mahurangi & Matakana • AC high value • Evidence of historical cultural tuna fishery A F E B D C B. Coromandel • East coast lots of fish – source populations? • Longfin eels C. Southern Hauraki • Waihou & Piako • Degraded • Sink populations inanga? • Source populations - smelt & torrentfish? Priorities & knowledge gaps • Mair (1902) account of fishing in lower Piako (3 miles inland) – Traditional funnel shaped net (tarawa) – Two lifts in ¾ hour – 581 eels, c.100 flounder, large numbers of yellow-eyed mullet, 60-70lb pilchards, snapper, kahawai, hundreds of young red cod, blue cod & large quantities of a kind of whitebait • WRC 1990 survey (2 miles inland, 8 fyke nets & 9 gill nets) caught 200 eels, 3 mullet, 17 common bullies & 1 marine species Any questions?
© Copyright 2024