Larval supply and recruitment of reef fish at 5 sites around Lord Howe Island were measured during November/December 2003 and January/February 2004. Light traps, artificial reef units (ARUs), and underwater visual censuses were used simultaneously. Two types of ARUs were trialed, Standardised Monitoring Units for the Recruitment of Fishes (SMURFs) and crevice collectors. Visual censuses involved taking photos of the habitat every 5m along a 25 x 2m fixed transect.
The results indicated that the catch efficiencies of the 2 ARUs varied depending on species. For example, Eviota spp. preferentially settled into crevice collectors, while Enneapterygius rufopileus (blackcheek threefin) preferred SMURFs. Spatial patterns of recruitment were influenced by larval supply only for E.rufopileus. The amount of suitable habitat was a good predictor of recruitment for Neoglyphidodon polyacanthus (multispine damsel).
To determine the relationship between larval supply and recruitment of reef fish populations at Lord Howe Island.
Heather Patterson and Steve Swearer were supervisors in this Honours project.
2 SMURFS and 2 crevice collectors were moored at 5 sites within the Lord Howe Island lagoon by SCUBA divers on 2003-11-15. SMURFS and collectors were cleared on 2003-12-09, 2004-01-24 and 2004-02-18. This was done by pulling them up onto the boat and vigorously shaking and rinsing them with seawater. Recruits were either identified to species in the field and released or preserved in 70% ethanol and identified by examination with a microscope in the laboratory.
2 light traps were deployed at the 5 sites on 8 nights of the first field trip (2003-11-20 to 2003-12-06) and 10 nights on the second trip (2004-01-21 to 2004-02-16). Light traps were placed 100m apart and the SMURFs and crevice collectors were alternated at 20m intervals between the 2 light traps. Larvae caught in the traps were collected between 8am and 10am the next morning and transferred to containers of seawater.
Light traps consisted of 3 main parts: the trap body, a removable collecting basket and a removable waterproof light and battery unit. The trap body had a single chamber, constructed from an aluminum frame fitted with clear perspex panels that tapered into a central vertical slit. The collecting basket had 1mm mesh windows cut into each face for drainage and was attached to the aluminum frame of the main body with quick release clamps. The light source was housed within the clear perspex tube, which was fixed to a watertight PVC cylinder containing a rechargeable sealed lead-acid battery and the electrical circuit. The light was activated by an infrared sensor, allowing the traps to operate continuously during the night.