Settlement behaviour of coral-reef fish larvae at subsurface artificial-reef moorings

Abstract

Artificial-reef units (rolls of plastic garden mesh) attached to subsurface floats were used to study settlement behaviour of larval reef fishes. These units were located 3, 5, 7 and 9 m above the bottom in water 15–19 m deep in the Great Barrier Reef Lagoon, 1 km from natural reefs. Larvae of 50 species (15 families) settled on these units. The nine most abundant reef-fish taxa were in the families Apogonidae, Blenniidae, Gobiidae, Monacanthidae, Pomacentridae and Tetraodontidae. The less abundant of these taxa (n = 4) settled uniformly. The more abundant taxa (n = 5) had clumped settlement. Four taxa preferred structurally complex reef units, whereas five showed no preference. Apogonids, gobiids, tetraodontids and a pomacentrid preferred deep units, one pomacentrid had no depth preference, and a blenniid and a monacanthid preferred shallow units. Experiments evaluated visual, olfactory and auditory cues that reef-fish larvae may use to locate and settle onto reefs. Visual cues (large white panels) did not enhance settlement. Experiments on olfactory cues (corals in vented containers) and auditory cues (‘the nocturnal chorus’ of tropical reefs) were compromised by low and highly variable settlement, but show the potential of the method. The advantages of subsurface moorings for study of settlement behaviour are discussed.

Using Aggregating Devices to Sample Fish Recruits Around Deep Shipwrecks: Experiments and Suggestions

“…These studies used sampling intervals smaller than the present study: 4 to 10 days (Schroeder, 1987), 2 days (Leis et al, 2002) and 7 days (Paiva et al, 2015), in addition to different positioning arrays and abundance calculations. Leis et al (2002) computes the sample mean just for the FADs in which individuals of were found, while Schroeder (1987) calculates the abundance in recruits/FAD/day. On the other hand, authors like Paiva et al (2015) do not report catches by FADs, just the total number of individuals per species per treatments.…”

“…The low efficiency of ARM model, compared to the SMURF, was unexpected, since several studies with ARM achieved relatively high recruits' catches (Schroeder, 1987;Leis et al, 2002;Paiva et al, 2015). These studies used sampling intervals smaller than the present study: 4 to 10 days (Schroeder, 1987), 2 days (Leis et al, 2002) and 7 days (Paiva et al, 2015), in addition to different positioning arrays and abundance calculations. Leis et al (2002) computes the sample mean just for the FADs in which individuals of were found, while Schroeder (1987) calculates the abundance in recruits/FAD/day.…”

“…Depth apparently did not have any influence in number of fish recruits per FAD, excluding the ARMs, where the few sampled fishes were found in devices placed on the bottom. FADs positioned closer to the bottom tend to aggregate similar total numbers of recruits, while significant differences between the samples usually occur between FADs positioned close the bottom to those from subsurface (Leis et al, 2002;Ammann, 2004), the latter tend to be preferred in studies focusing on only one species or in groups of similar USING AGGREGATING DEVICES TO SAMPLE FISH RECRUITS AROUND DEEP SHIPWRECKS: EXPERIMENTS AND SUGGESTIONS species in view its high aggregation rates for these species (e.g. Ben-David & Kritzer, 2005;Caselle et al, 2010).…”

“…ARM model was modified from Schroeder (1987). It was successfully used by Leis et al (2002) and its name created by Paiva et al (2015). The structure of the ARMs was composed of a spiral cylindrical frame (0.6 m length x 0.20 m diameter) of black fencing plastic net with mesh size of 2 x 2 cm and stainless-steel snap-clips tied to frame (Figure 2B and 2C).…”

“…The "Schroeder's basket", as it was called, was used to characterize the different young fish communities at different depths (Leis et al, 2002). Ammann (2004) developed the Standard Monitoring Units for Reef Fishes (SMURFs) that resembled the Schroeder's basket, but with your interior composed of randomly folded nets, enabling greater complexity than the previous FAD model.…”