Ecophysiological assessment of the little fish of São Tomé island using rna:dna ratios

McDonald, Lindsey Jean

http://hdl.handle.net/10400.1/27033

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Authors

McDonald, Lindsey Jean

Advisor(s)

Baptista, Vânia

Cruz, Joana

Abstract(s)

In the many rivers of São Tomé Island lives a group of amphidromous fish known collectively as “peixinho” or “little fish” when at the post-larval stage. The species that make up this group include Awaous lateristriga, Sicydium brevifile and Sicydium bustamantei. Although these species are locally very important both as a source of income and protein, there is still little knowledge available about them. To obtain information about their ecophysiological condition, this study looked at the standardized RNA:DNA ratio (sRD), DNA concentrations and RNA concentrations of these species, comparing them between different rivers, the Iô-Grande, Lembá, Martim Mendes, and Paga Fogo in the wet and dry seasons. During the dry season when food availability can be expected to be lower, sRD were significantly lower for Sicydium species, indicating a poorer physiological condition than in the wet season. DNA and RNA concentrations were found to be higher for all species during the dry season. Looking at these concentrations relative to one another, this could also indicate poorer physiological condition. Generally, results were consistent between species and rivers but due to sampling limitations, a robust comparison could not be made between the three species and the four rivers. This study provides insight into the ecophysiological status of these three fish species in São Tomé Island rivers, which can help to develop conservation and management strategies.