Biology of a marine estuarine-opportunist fish species in a microtidal estuary, including comparisons among decades and with coastal waters

Abstract

The biological characteristics of a marine and macrophyte-associated species (Pelates octolineatus) in a large microtidal, eutrophic estuary in 2008-10 were determined. Comparisons are made with those of individuals remaining in coastal waters and during two earlier periods in the estuary when plant biomass differed markedly. P. octolineatus start entering the Peel-Harvey Estuary in mid-summer, soon after metamorphosis, with many remaining there until autumn when they are ~15 months old.These individuals, and older fish that re-entered the estuary in summer, then return to the sea where they spawn from late spring to early summer. Most P. octolineatus in the estuary were less than or equal to the length at maturity and all were <4 years old, whereas individuals up to 10 years old were caught in coastal embayments, emphasising that the estuary acts mainly as a nursery for this terapontid. Growth in the estuary was seasonal and peaked earlier and was greater than in marine waters. Abundance of P. octolineatus in the estuary was greater in 2008-10 and 1980-81 than in 1996-97, when macrophytes were less abundant. The results demonstrate how a marine estuarineopportunist can benefit from using both estuaries and coastal waters as a nursery area and capitalise on variations in environmental conditions.

Decadal changes in the ichthyofauna of a eutrophic estuary following a remedial engineering modification and subsequent environmental shifts

“…Mean water temperature exhibited similar pronounced seasonal changes at all sites and in each year, declining from maxima of ~25 ºC in summer to minima of ~14 ºC in winter and then rising in spring (Veale et al, 2016).…”

“…This energy source is used by the wide range of marine fish species that enter estuaries in appreciable numbers, particularly during early life. Thus, in comparison with their natal environment, the juveniles of these species grow more rapidly and, through the presence of fewer large piscivores, are less susceptible to predation (Blaber, 1980;Le Pape et al, 2003;Yamashita et al, 2003;Veale et al, 2016). Estuaries have therefore often been considered as important nursery areas for fish (Blaber and Blaber, 1980;Beck et al, 2001;Able and Fahay, 2010;Sheaves et al, 2014).…”

The Contrasting Ecology of Temperate Macrotidal and Microtidal Estuaries

“…seagrass in the clearer waters of microtidal estuaries (Odum & Heald 1972, Blaber & Blaber 1980, Robertson & Blaber 1992, Jackson et al 2001a). The extensive use of estuaries by the juveniles of marine species has often been regarded as facilitating more rapid growth and thus increasing survival beyond that which could be achieved by remaining in their natal environment (Sogard 1992, Le Pape et al 2003, Yamashita et al 2003, Veale et al 2015.…”

“…The estuary thus acts as a nursery area for these species (Blaber & Blaber 1980, Beck et al 2001, with the abundant food available in these systems facilitating rapid growth and thereby a reduction in their susceptibility to predation (Le Pape et al 2003, Yamashita et al 2003, Veale et al 2015. Numerous marine estuarine-opportunists also use sheltered nearshore marine environments as well as estuaries as nursery areas, with the relative use of these two environments varying among species and according to the extent that one or both of those environments are present in the area , Gillanders et al 2003, Able 2005, Able & Fahay 2010.…”

Social, spatial and isotopic niche partitioning identify an estuarine community of bottlenose dolphins as a discrete management unit

“…The channels are likely to have larger quantities of high calorific value fish, such as Pelates octolineatus and Arripis truttaceus (McCluskey, Bejder & Loneragan, 2016), available during this time. P. octolineatus is relatively abundant in the Peel-Harvey Estuary (Loneragan et al, 1986;Potter et al, 2016) and mature individuals emigrate through the channels to spawn in the marine environment in autumn (Veale et al, 2016). In contrast, adult…”