Abstract
Seven species of the family Sciaenidae have been reported inhabiting bottom waters of the Rio de la Plata estuary. Of these juvenile stripped weakfish (Cynoscion guatucupa), king weakfish (Macrodon ancylodon), whitemouth croaker (Micropogonias furnieri) and banded ground drum (Paralonchurus brasiliensis) are by far the most abundant. These species are also important prey of several top-predator species among large fishes, seabirds and mammals. In this study we provide new information regarding otolith morphology and body size relationships of juvenile sciaenid fish. The sagittae morphology of juvenile sciaenids showed strong changes in the course of their development (e.g. in overall shape and development of concrescences on the outer surface). Analysing the morphometric relationships, we concluded that otolith length and otolith mass are good indicators of fish standard length and fish weight in all species. If otolith length or mass is used to estimate fish length, the regression explained more than 97% of the variation in all species. All equations relating fish standard length and fish weight for juvenile stages of the species studied explained a very large proportion of the variance in the data. These data will help researchers studying food habits of top predators to determine size and weight of usually juvenile fish-prey from length, broad and/or weight of recovered otoliths.
Highlights
The family Sciaenidae is important in both tropical and subtropical waters; sciaenid species are usually common and abundant in estuarine waters, which are often used for spawning of adult and growth of juvenile individuals (Corrêa and Vianna, 1993; Acha et al, 1999)
We provide new otolith images from juvenile fish, usually away from adult morphology, to be used as and aid for identifying fish species
FIG. 1. – Terminology used throughout the text in the descriptions of otoliths of four sciaenid species from the Río de la Plata estuary
Summary
The family Sciaenidae is important in both tropical and subtropical waters; sciaenid species are usually common and abundant in estuarine waters, which are often used for spawning of adult and growth of juvenile individuals (Corrêa and Vianna, 1993; Acha et al, 1999). Seven species of this family have been reported as inhabiting bottom waters of the Río de la Plata estuary (34o-36oS, 54o-57oW) Of these juvenile stripped weakfish, Cynoscion guatucupa (Cuvier, 1830), king weakfish, Macrodon ancylodon Schneider, 1801, whitemouth croaker, Micropogonias furnieri (Desmarest, 1823) and banded ground drum Paralonchurus brasiliensis (Steindachner, 1875) are by far the most abundant (Cousseau, 1985; Lasta, 1995). These species are important prey of top-predator seabirds, such as the common tern, Sterna hirundo (Linnaeus, 1758). Fishery biologists have been using this information as an indirect indicator of fish distribution and for quantifying the potential effects of natural predation (Corrêa and Vianna, 1993; Mauco et al., 2001)
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