Quantifying Mesophotic Fish Assemblages of Hawai‘i’s Au‘au Channel: Associations With Benthic Habitats and Depth

Mesophotic reefs (30–150 m) occur in the tropics and subtropics at depths beyond most scientific diving, thereby making conventional surveys challenging. Towed cameras, submersibles, and mixed-gas divers were used to survey the mesophotic reef fish assemblages and benthic substrates of the Au‘au Channel, between the Hawaiian Islands of Maui and Lāna‘i. Non-parametric multivariate analysis: Non-metric Multidimensional Scaling (NMDS), Hierarchical Cluster Analysis (HCA), Multi-Response Permutation Procedure (MRPP), and Indicator Species Analysis (ISA) were used to determine the association of mesophotic reef fish species with benthic substrates and depth. Between 53 and 115-m depths, 82 species and 10 genera of fish were observed together with 10 types of benthic substrate. Eight species of fish (Apolemichthys arcuatus, Centropyge potteri, Chaetodon kleinii, Chromis leucura, Chromis verater, Forcipiger sp., Naso hexacanthus, and Parupeneus multifasciatus) were positively associated with increasing depth, Leptoseris sp. coral cover, and hard-bottom cover, and one species (Oxycheilinus bimaculatus) of fish was positively associated with increasing Halimeda sp. algae cover. Fish assemblages associated with rubble were not significantly different from those associated with sand, Montipora coral beds and Leptoseris coral beds, but were distinct from fish assemblages associated with hard bottom. The patterns in the data suggested two depth assemblages, one “upper mesophotic” between 53 and 95 m and the other deeper, possibly part of a “lower mesophotic” assemblage between 96 and 115 m at the edge of the rariphotic and bottomfish complex.

SUMBER DAYA IKAN KARANG DI TAMAN WISATA ALAM GILI MATRA, LOMBOK BARAT

Keanekaragaman dan kelimpahan ikan karang adalah indikator yang baik untuk menilai secara dini adanya dampak pada ekosistem terumbu karang dari sebab kegiatan manusia yang tinggal di sekitar Taman Wisata Alam Laut. Tujuan penelitian ini adalah untuk mengindentifikasi sumber daya ikan karang yang ditinjau dari sisi keanekaragaman jenis, kepadatan individu, komposisi dan biomassa ikan karang dari kelompok fungsional ikan karang. Penelitian dilakukan pada September 2014 dengan metode sensus visual bawah air. Berat ikan didapat dengan cara mensubsitusikan panjang ikan ke rumus panjang berat (W= aXb). Hasil penelitian menunjukkan bahwa terdapat sedikitnya 27 spesies ikan indikator dan 84 spesies ikan target dari 16 famili. Kelompok ikan herbivora dijumpai 36 spesies dari 3 famili, ikan karnivora dijumpai 43 spesies dari 10 famili dan ikan planktivora 5 spesies dari 3 famili. Urutan dari 10 terbesar ikan karang yang dijumpai terdiri dari Ctenochaetus striatus (13 ekor/350m2), Mulloidichthys flavolineatus (10,25 ekor/350m2), Acanthurus olivaceus (8,4 ekor/350m2), Parupeneus multifasciatus (6,5 ekor/350m2), Myripristis kuntee (5,5 ekor/350m2), Kyphosus cinerascens (5,25 ekor/350m2), Lutjanus kasmira (5,13 ekor/350m2), Acanthurus leucocheilus (4,9 ekor/350m2), Scarus ghobban (4,6 ekor/350m2), Parupeneus bifasciatus (4,6 ekor/350m2). Rata-rata kelimpahan ikan karang tertinggi 0,46 individu/m2 dan terendah 0,06 individu/m2. Rata-rata biomassa ikan karang 81,2 kg/350m2 dan terendah 4,69 kg/350m2. Ikan karang target tersedia 1.126 kg per hektar. Reef fish diversity and abundance are good indicators to assess early for impacts on coral reefs ecosystem resulted from human activities living in the adjacent waters of the Gili Matra Tourism Marine Park. The study objective is to identify reef fish resources with regards to species deversity, density, composition and biomass of reef fish functional groups. The work was carried out in September 2014 with a census visual method. Body weight is derived from putting in fish length to weight-length formula (W=aLb). The results show that there were at least 27 species of coralivorous fishes and 84 species of target fish belong to 16 families. There were 36 herbivorous fishes of three families, 43 carnivorous fishes of ten families, and 5 planktivorous fishes of three families. The ten greatest of reef fish biomass were consisted of Ctenochaetus striatus (13 individual/350m2), Mulloidichthys flavolineatus (10.25 individual/350m2), Acanthurus olivaceus (8.4 individual/350m2), Parupeneus multifasciatus (6.5 individual/350m2), Myripristis kuntee (5.5 individual/350m2), Kyphosus cinerascens (5,25 individual/350m2), Lutjanus kasmira (5.13 individual/350m2), Acanthurus leucocheilus (4.9 individual/350m2), Scarus ghobban (4.6 individual/350m2), Parupeneus bifasciatus (4.6 individual/350m2). The abundance of individual reef fish was ranged from the highest of 0.46 individu/m2 to the lowest of 0.06 individual/m2. The biomass of reef fish was ranged from the highest of 81.2 kg/350m2 to the lowest of 4.69 kg/350m2. The target fish was available for 1.126 kg per hectar.