Natural values of the Solitary Islands Marine Park - Marine Parks ...

6 Pelagic ecosystemsOcean currents are a major influence on open ocean habitats in the marine park. TheEast Australian Current is active during the warmer months, and at times it movesclose inshore, bringing tropical organisms from the southern Great Barrier Reef. Thiscreates conditions which enable many tropical species to settle in the marine park.During the cooler months, the marine park is dominated by inshore currents movingnorthwards. These currents bring temperate species into the marine park, and createcooler conditions favouring the growth of temperate marine life.Open ocean habitats in the marine park are inhabited by a wide diversity of marineorganisms including whales and dolphins, large pelagic fish (Figure 45), and jellyfishand other invertebrates. Planktonic processes occurring in open oceans are importantto most marine organisms, as tiny planktonic plants and animals are a rich source offood.There is a close association between species in open oceans and other marinehabitats. Bottom-dwelling fish species rely on pelagic bait species, linking pelagic foodchains with those of seafloor communities (Smale 1992). Pelagic and mesopelagicspecies (species living at depths between 180 and 900 metres) are an integral partof marine communities found in the marine park. Pelagic species provide juvenilesas a source of food and to propagate their species; provide food through fish spawn;recycle nutrients; graze down algal beds; and prey on weak, sick and old individuals.There are seasonal influences on pelagic species of interest to fishers includingmackerel species being present in the warmer months (usually from January to May).Figure 45.Dolphinfish.