Habitat selection by emperor fish larvae

One of the great puzzles of coral reef fish ecology is how pelagic larvae locate the habitat in which they settle. The present study explored whether offshore emperor fish (Lethrinidae) larvae selected a specific reef and/or habitat at settlement. Although older juveniles are known to use back-reef seagrass beds as a potential nursery habitat, information is scarce regarding pre-settlement larvae. Using light traps anchored on the reef slopes at seagrass-replete and seagrass-free reefs (lshigaki Island, Japan), lethrinid larvae were sampled weekly from April to June 2008. Larval abundance in light traps was similar on the 2 reef types. This result implies that lethrinid larvae did not or could not differentiate between the presence or absence of seagrass before settlement. However, in the laboratory, larvae collected from both reef types selected seagrass substrate rather than bare substrate or coral. In underwater visual censuses, newly settled juveniles were not observed on the seagrass-free reef, whereas they were abundant on the seagrass-replete reef. Together, these findings suggest that lethrinid larvae did not settle near the seagrass-free reef but rather preferentially settled near the seagrass-replete reef

Spatial variability in habitat associations of pre- and post-settlement stages of coral reef fishes at Ishigaki Island, Japan

Successful settlement of pelagic fish larvae into benthic juvenile habitats may be enhanced by a shortened settlement period, since it limits larval exposure to predation in the new habitat. Because the spatial distribution of marine fish larvae immediately prior to settlement versus during settlement was unknown, field experiments were conducted at Ishigaki Island (Japan) using light trap sampling and underwater visual belt transect surveys to investigate the spatial distribution patterns of selected pre- and post-settlement fishes (Acanthuridae, Pomacentridae, Chaetodonidae and Lethrinidae) among four habitats (seagrass bed, coral rubble, branching coral and tabular coral). The results highlighted two patterns: patterns 1, pre- and post-settlement individuals showing a ubiquitous distribution among the four habitats (Acanthuridae) and pattern 2, pre-settlement individuals distributed in all habitats, but post-settlement individuals restricted to coral (most species of Pomacentridae and Chaetodontidae) or seagrass habitats (Lethrinidae). The first pattern minimizes the transition time between the larval pelagic stage and acquisition of a benthic reef habitat, the latter leading immediately to a juvenile lifestyle. In contrast, the second pattern is characterized by high settlement habitat selectivity by larvae and/or differential mortality immediately after settlement

Sustaining environmental integrity in the midst of intensified aquaculture development

The escalating aquaculture production from Southeast Asia during the past decades seems inevitable notwithstanding its significant contribution to economic growth and guaranteed food security of the countries in the region. Despite its good prospects, the region’s aquaculture sector is being confronted with various issues that should be addressed to enable it to develop sustainably and contribute unceasingly to poverty alleviation in the region. Responsible aquaculture has been practiced in the region as means of easing the crisis in capture fisheries; however, this has to be matched with effective approaches that address concerns on the fishery resources that are deteriorating. Resource enhancement of economically important aquatic species has been considered as one of the effective approaches that would help protect and restore the aquatic resource habitats and stocks, the latter connotes stock enhancement. As could be gleaned from the current scenario of fisheries in the Southeast Asian region, the recurring over-exploitation of common natural resources has affected the livelihoods of fishers and coastal communities. The imbalanced extraction of natural aquatic resources and natural recruitment has worsened through the years and if left unabated could result in the extinction of many of the region’s endemic aquatic species. It is for such consequences that the Aquaculture Department of the Southeast Asian Fisheries Development Center, while intensifying its efforts in developing sustainable aquaculture, is also promoting resource enhancement as these two approaches are expected to enhance the region’s fishery resources and food security in view of their perfect roles in improving the productivity of aquatic stocks and status of the natural habitats. Nonetheless, aquaculture techniques have always been used to facilitate the stock enhancement of commercially important, threatened and endangered aquatic species. The National Oceanic and Atmospheric Administration of the USA defines stock enhancement as “restoration aquaculture” or the release of hatchery-bred juveniles of fish and shellfish to the wild, and considers this approach as a management tool to recover depleted stocks due to overfishing and habitat loss. The Food and Agriculture Organization of the United Nations has demonstrated that stock enhancement is a type of culture based fisheries since part of the life cycle of certain aquatic species is being controlled in hatcheries before the seeds or juveniles are transplanted or released into open waters — freshwater or brackishwater or marine environments — and allowed to propagate or grow on natural foods until reaching harvestable size

Stock enhancement of abalone, Haliotis asinina, in multi-use buffer zone of Sagay Marine Reserve in the Philippines

Donkey's ear abalone (Haliotis asinina) is a gourmet seafood export of the Philippines but its wild stock is at risk due to high fishing pressure. This paper aims to show evidences that abalone seeds produced in hatcheries can be used to rehabilitate its fisheries in multi-use buffer zones of marine reserves. This study released hatchery-reared abalone juveniles in a community-based resource enhancement site located in multi-use reef surrounding Molocaboc. This island is populated by fisherfolks who participated in protecting the 4000 m2 coralline release site. Molocaboc Reef comprise the buffer zone of Sagay Marine Reserve in Negros Occidental province in central Philippines. Data obtained during monthly monitoring of the release site from 2011 to 2016 showed that hatchery-reared abalone established together with its wild counterparts. Baseline wild abalone catch per unit effort (CPUE = 3 divers 1 h fishing) is 0.005/100 m2 in 2011. Mean monthly CPUE after release increased to 53 hatchery-reared and wild individuals combined. The mean shell length, body weight and body mass index of the hatchery-reared individuals (6.4 cm, 70.9 g, 10.5 g/cm) is not significantly different from those of the recovered wild stocks (6.9 cm, 85.0 g, 12.0 g/cm). The stocks recovered in the midst of undisrupted fishing activities in areas immediately outside and beyond the release site. Thus, mass production of seeds of overfished species is advised to repopulate degraded fisheries, improve catch of fisherfolks living within buffer areas of marine reserves and contribute to production and trade of high-value species