Between waterfalls and coral reefs: assessing the overlooked Hawaiian
estuarine fish habitat
Peyton, Kimberly A.1; Sakihara, Troy1; Shimoda, Troy1; Nishiura, Lance1; Shindo, Timothy1; Hau, Skippy1; Higashi, Glenn1; Lapp, Eko1; Infante, Dana2; Tingley, Ralph2; Tsan,
Yin-Pahn2; Mackenzie, Rich3; Smith, Gordon4 1Hawaii Division of Aquatic Resources; 2Michigan State;
3USFS; 4Hawaii FHP
Overarching goal: To describe and understand how estuaries in Hawaii function as juvenile fish habitat.
Aquatic Habitat Assessments in Hawaii The Hawaii Fish Habitat Partnership has participated in developing the following aquatic habitat assessments:
• Atlas of Hawaiian Watersheds
• Statewide Inventory of Barriers to Fish Passage
• Hawaii Portion of the 2010 National Assessment of Fish Habitat
• Marine assessments linking upstream/downstream habitat condition – initiated in 2014
• 9 streams along the North Hilo and Hamakua districts of Hawaii Island
• streams span a steep precipitation gradient • Started regionally now expanding to state
wide stream ecological classifaqtio system
Richard MacKenzie [email protected]
Hawaiian estuaries
C. Glenn UH-Manoa SOEST
Undertaking a census of Hawaiian estuaries
Juvenile habitat – Cast net surveys
10 sites total for 3 years – 4 times per year Kauai, Oahu, Maui and Hawaii Island
Results all years and sites pooled
16,864 fish sampled >170 kilograms (>376 pounds)
75 species sampled
63 fish species 32 families
12 invertebrate species 7 families
Hawaiian estuaries are diverse
Relative Abundance
Kuhlia xenura
Valamugil engeli
Atherinomorus insularum
Mugil cephalus
Mulloidichthys flavolineatus
Herklotsichthys quadrimaculatus
Sarotherodon melanotheron
Polydactylus sexfilis
Caranx ignobilis
Caranx melampygus
Acanthurus triostegus
Scomberoides lysan
Kuhlia sandvicensis
Selar crumenophthalmus
Abudefduf abdominalis
Hemichromis elongatus
Sport fish and invasive fish are the most abundant juveniles
Relative biomass is also composed of sport fish and invasive fish
Relative Biomass
Kuhlia xenura
Valamugil engeli
Mulloidichthys flavolineatus
Mugil cephalus
Sarotherodon melanotheron
Herklotsichthys quadrimaculatus
Atherinomorus insularum
Polydactylus sexfilis
Acanthurus triostegus
Caranx ignobilis
Caranx melampygus
Kuhlia sandvicensis
Abudefduf abdominalis
Scomberoides lysan
Selar crumenophthalmus
Hemichromis elongatus
Invasive fish are a problem in estuaries
Relative Abundance
Native speciesInvasive species
Invasive species make up an even greater proportion of relative biomass because adults co-occur with juveniles.
Relative Biomass
Native speciesInvasive species
Emergent plants are important habitat for juvenile fishes
Hawaii is a sedge based system
Urochloa mutica California grass/para grass
Objective: conserve and restore juvenile fish habitat
How do these two habitats function as juvenile fish habitat?
Urochloa mutica California grass/para grass
Mapped the invasion of
California grass in Hilo estuary
• Opportunistic study • Original question compared relative
abundance mullet species • 9-year study • Concluded study because of
sampling access problems • Growth rate: 1.3 - 36.0 m2 d-1
CPUE declined for
juvenile native mullet
with the invasion of California
grass
Native species
For juvenile invasive
mullet CPUE is
independent of the
invasion of California
grass Exotic species
California grass smothers juvenile striped mullet habitat
Native species Exotic species
Striped mullet feed on benthic diatoms
Open canopy formed by sedges creates benthic diatom habitat
Mahalo