Identifying reef fish nursery habitats on subtropical rocky reefs in the Southwestern Atlantic

• Availability of nursery habitats can potentially limit adult populations of reef fish. Suitable nursery habitats are often shallow and located close to shore, and in many cases overlap with anthropogenic stressors and human activities. For proper management of reef fish communities it is therefore important to identify these habitats and minimize conflicts of habitat use in time and space. To identify potential spatial and temporal patterns of nursery habitat use, the reef fish communities on subtropical rocky reefs in the South western Atlantic were surveyed with under water visual census. Surveys were performed in summer and winter months during two years, along a depth gradient on marginal reefs and in seasonal Sargassum macroalgal beds. No clear patterns in total juvenile abundance and distribution were distinguished between seasons, although some families occurred in significantly higher abundances in summer months (Haemulidae and Sparidae). There were large variances in juvenile abundance between the two surveyed summers, with low total abundance in the summer of 2017, which could be linked to weak upwelling in the area and hampered growth of Sargassum. Similar to in other locations globally, climatic events that affect biomass of Sargassum may hence have large effects on fish recruitment also in the South western Atlantic. In general, shallow areas in sheltered bays had higher abundances of juvenile fish, especially when Sargassum was present in these locations. Spatial patterns of acanthurids and labrid scarinae, were more homogenous compared to those of tropical reefs in the South western Atlantic, where Sargassum beds harbor significantly more juveniles than other habitats. We suggest that fish in sub-tropical rocky reef environments in the South western Atlantic have access to less habitat diversity and complex substrate to use as nursery areas, and thus shallow, sheltered and vegetated habitats are critical for many species. Additionally, those habitats are also the most threatened by human uses demanding proper management.

Ämnesord

NATURVETENSKAP  -- Biologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences (hsv//eng)

Nyckelord

Marine Ecology

marin ekologi

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