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?