Habitat partitioning by juvenile fishes in a temperate estuarine nursery, South Africa

Abstract

Summary:Multiple habitats were investigated in a known fish nursery area to further understand habitat partitioning among juveniles in the lower reaches of the warm temperate, permanently open Swartkops Estuary, South Africa. Fishes were collected using a 30-m seine net with a mesh size of 10 mm in sand, mud, creek and vegetated habitat types. Each habitat type was sampled in two locations twice per season from February 2013 to January 2014. Shallow-water creeks and vegetated habitats with coverage of Zostera capensis and Spartina maritima were found to be important use areas for numerous solely estuarine and marine estuarine-dependent species. This was evidenced by the high species diversity, abundance and size range per species occurring in these habitats. Seasonal trends were similar to those in previous studies worldwide, where higher abundances of juveniles of marine estuarine-dependent species coincided with summer recruitment into estuarine nurseries. However, recruitment appears to begin as early as late winter in some species, a phenomenon probably linked to a warming climate. Both resident species and those utilizing the area as a nursery area show a large degree of plasticity in habitat use in the lower reaches of the estuary, which became apparent when multiple habitats were compared. The drivers of these patterns involve a complex interaction of species, habitat type, behaviour, feeding, predator avoidance and physicochemical factors occurring in the estuary.Keywords: Ichthyofauna; nursery grounds; community composition; estuary association; recruitment. Segregación de hábitat en juveniles de peces en una región de cría de un estuario templado, SudáfricaResumen: Con objeto de entender mejor la segregación de hábitats en juveniles de peces se investigaron múltiples hábitats en una zona de cría en la parte baja del estuario del Swartkops (Sudáfrica) (de tipo templado-cálido y abierto permanentemente). Los peces fueron recolectados con una red de cerco de 30 m, con malla de 10 mm de abertura, sobre fondos de arena, barro, arroyos yhábitats con vegetación. Cada tipo de hábitat se muestreó en dos lugares, dos veces por estación, de febrero 2013 a enero 2014. Se observó que los arroyos de aguas poco profundas y los hábitats con cobertura de Zostera capensis y Spartina maritima eran áreas importantes para numerosas especies exclusivamente estuáricas y para especies marinas dependientes de los estuarios. Esto se evidenció por la gran diversidad de especies, abundancia y rango de tallas de las especies que aparecieron. Las tendencias estacionales fueron similares a los de estudios anteriores en todo el mundo, donde las más altas abundancias de juveniles de las especies marinas que dependen de los estuarios coincidieron con el reclutamiento de verano dentro del estuario. Sin embargo, en algunas especies el reclutamiento parece comenzar más pronto, a finales del invierno, un fenómeno probablemente ligado al calentamiento climático. Tanto las especies residentes en el estuario como las que lo utilizan como área...

The effects of hypersalinity on the growth and skeletal anomalies of juvenile Cape stumpnose, <em>Rhabdosargus holubi</em> (Sparidae)

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Mediterranean nekton traits: distribution, relationships and significance for marine ecology monitoring and management

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