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Mangroves as nursery habitats for Galapagos reef fishes

Abstract:

Mangroves offer key ecosystem services such as the provision of feeding, breeding, and nursery grounds to marine fish populations. The role of mangroves as fish nursery habitats is not ubiquitous and depends on factors such as species, geographic location, and environmental conditions. Studies of this nursery role for fish species are limited in the Tropical Eastern Pacific and particularly scarce for the Galapagos Islands. We used underwater visual censuses to survey fish species composition within mangrove forests and adjacent shallow rocky reefs across 6 of the Galapagos Islands. Adult densities of 3 commercially important reef fishes (Lutjanus argentiventris, L. novemfasciatus, and Mycteroperca olfax) were also surveyed in adjacent deep rocky reefs to investigate the relative importance and potential of mangroves in supporting their populations. Our study provides evidence that mangroves play a role as nursery habitats for reef fish species. Specifically, we identified Eucinostomus dowii, L. argentiventris, Mugil spp., Mycteroperca olfax, Sphoeroides annulatus, Stegastes arcifrons, and Scarus ghobban as mangrove nursery species, as their juvenile densities were significantly higher in mangroves than in shallow rocky reefs. Additionally, 19 other fish species, primarily juveniles, were exclusively observed within mangrove habitats. We found that the extent of mangrove perimeter within 10 km of deep reefs positively influenced the densities of adult L. argentiventris and M. olfax. Our results argue for the need to consider nursery ecosystem function in the design and management of the Galapagos Marine Reserve, since mangroves will directly contribute to the fisheries management of economically important species.