An evaluation of the relative nursery value of sandy shore surf zones and estuary mouths in tropical North Queensland, Australia

Lheknim, Vachira (1995) An evaluation of the relative nursery value of sandy shore surf zones and estuary mouths in tropical North Queensland, Australia. PhD thesis, James Cook University of North Queensland.

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This study attempts to assess the relative nursery value of tropical intertidal habitats. A new definition of a nursery habitat is proposed, based on persistence, growth and survival. Based on this definition, this thesis examines the relative nursery value of two intertidal habitats based on analyses of temporal and spatial abundance patterns, feeding success and growth rates. The relative value of these parameters for determining nursery area value is also evaluated.

Fishes were sampled bimonthly with seine nets (5 mm mesh) in three selected sandy shore surf zones and three estuary mouths from the summer of 1992 to the winter of 1994. The presence of the juvenile stage of 126 species in intertidal collections from both habitats indicated that these areas are potentially important habitats for young fishes. Nested ANOVAs for species richness, total abundance and total fish biomass revealed no significant differences between sandy shore surf zones and estuary mouths. However, marked seasonal differences between summer and winter assemblages were apparent, with higher total abundance and species richness in early summer which were likely to be related to recruitment episodes. Cluster analysis suggested there were relatively strong similarities between sandy shore surf zones and estuary mouths, with little similarity between seasons.

Four selected species which occur at both habitats were selected for detailed analyses of abundance, biomass, feeding success and growth rate determination: Stolephorus nelsoni, Sillago analis, Leiognathus splendens and Valamugil seheli. Analysis of variance detected no significant differences in numbers of individuals or biomass of each species between sandy shore surf zones and estuary mouths.

The stomach contents of S. nelsoni, S. analis and L. splendens were examined. For all species, estuary mouth fishes had a relatively high proportion of stomachs which contained food, and a greater gut fullness than fishes taken from sandy shore surf zones. It is suggested that there may be a potential for food limitation or sub-optimal feeding conditions in sandy shore surf zones. Age-length relationships for S. nelsoni, S. analis, L. splendens and V. seheli were determined by using otolith increment counts. Daily deposition was validated in S. analis, L. splendens and V. seheli and assumed for S. nelsoni. A similar age at length relationship in both estuary mouths and sandy shore surf zones was evident in all selected species. This suggests that habitat differences may not account for growth rate in these selected species.

In conclusion, for the study species examined, estuary mouths have a relatively higher nursery value than sandy shore surf zones. The relative value of nursery habitats in the tropics is likely to be species and age specific. Food accessibility may influence the value of nursery areas, but alone it is a poor predictor of nursery function.

Item ID: 33777
Item Type: Thesis (PhD)
Keywords: abundance; Althus Creek; Bohle River; Cleveland Bay; estuaries; feeding; fishes; growth; habitat; Halifax Bay; intertidal areas; juveniles; larvae; nursery grounds; Pallarenda Beach; recruitment; Ross River; Saunders Beach; species diversity; Toolakea Beach
Date Deposited: 21 Jul 2015 04:34
FoR Codes: 05 ENVIRONMENTAL SCIENCES > 0501 Ecological Applications > 050102 Ecosystem Function @ 50%
06 BIOLOGICAL SCIENCES > 0602 Ecology > 060205 Marine and Estuarine Ecology (incl Marine Ichthyology) @ 50%
SEO Codes: 96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960808 Marine Flora, Fauna and Biodiversity @ 100%
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