Short-term and long-term influences of the immigration of postlarval banana prawns Penaeus merguiensis, into a mangrove estuary of the Gulf of Carpentaria, Australia

Abstract

Postlarval Penaeus merguiensis de Man were sampled regularly at the mouth of the Norman River estuary in the south-eastern Gulf of Carpentaria, Australia. from 1975 to 1979. A grid of stations up to 10 km offshore from the estuary mouth was also occupied over a 24 h period during November 1978. In these offshore stations, postlarvae migrated vertically in the water column in response to changes in tidal height, rising to near the surface just before low tide. Postlarvae entered the estuary throughout the flood tide with a peak in abundance occurring at the time of maximum current, regardless of time of day or night. During the monsoonal wet season (Dec-Mar), when estuary salinities were lower, postlarvae occurred deeper in the water column. Over the 4 yr of sampling, immigration on a day-to-day basis was extremely variable but a consistent spring-neap tidal cycle could be demonstrated. More postlarvae immigrated during the spring-tide period than during the neaps, although the pattern was complicated by a larger peak associated with every second spring tide (27.32 d). Although difficult to separate from tidal phase changes, lunar changes per seappeared to be less important than the relation between tidal phase changes and timing of moonset and moonrise. Immigration was restricted to the warmer months between October and April each year, with a large pulse of recruits occurring usually in spring (Oct-Nov) and a less consistent pulse occurring in autumn (Mar-May). Inter-annual variations were also large and it was suggested that these year-to-year differences were related to the amount of rainfall recorded during the previous wet season (9 mo earlier) and the associated changes in salinity, temperature, nutrients and abundance of adult prawns. Over larger time scales, both size and developmental stage (number rostra1 spines) were directly related to postlarval abundance. Thus, postlarvae tended to be larger and more well developed during spring and autumn of each year, and were also larger during years of higher immigration rates. Increased growth as well as survival in years following good rainfall and enrichment is suggested.

Natural or Artificial? Habitat-Use by the Bull Shark, Carcharhinus leucas

“…The natural estuarine habitats provide nurseries for many commercially important species, including prawns, crabs, fish and sharks [17], [18], [19], and are ecologically important to various stages in the lifecycle of sharks (e.g. [20], [21], [11]).…”

The population dynamics of Metapenueus ensis (Crustacea: Decapoda: Penaeidae) in a traditional tidal shrimp pond at the Mai Po Marshes Nature Reserve, Hong Kong

“…the Pearl River estuary. Moreover, heavy rainfall during the summer months exaggerates the salinity gradient and may enhance the immigration of larvae into the estuarine nursery areas (Staples & Vance, 1985). Excessive rainfall may, however, reduce the area of a salinity regime suitable for successful settlement and growth of penaeid larvae (Barrett & Ralph, 1976;Garcia & Le Reste, 1981).…”

Transport of Farfantepenaeus Aztecus Postlarvae in Three Lagoon-System Inlets in the Southwestern Gulf of Mexico

“…Several studies have shown evidence that penaeid post-larvae migrate vertically as a means to enhance recruitment to estuaries (Staples & Vance, 1985;Forbes & Benfield, 1986;Dall et al, 1990). Tidally based endogenous rhythms with peaks of movement around flood tide have been found for several species (Copeland & Truitt, 1966;Garcia & Le Reste, 1981;Mair et al, 1982;Forbes & Benfield, 1986).…”