A description of the early life history stages of the kob, Argyrosomus hololepidotus (Pisces: Sciaenidae), from southern Africa

The larval development of the kob, Argyrosomus hololepidotus is described and illustrated from a series of specimens collected in Algoa Bay, South Africa. Larvae are moderately deep bodies (BD = 30% BL) with a convex dorsal profile and trunk tapering to a narrow caudal peduncle. The head is large, increasing from 22% BL in preflexion larvae to 35% BL in juveniles. Pre-anal length increases from 37% BL in preflexion larvae to > 60% in juveniles. Notochord flexion occurs at 5-6 mm BL. Argyrosomus hololepidotus larvae are characterized by melanophores behind the head, at the anal fin base, on the caudal fin, on the abdomen, in the angle of the jaw and at the jaw isthmus. Medio-lateral pigmentation increases markedly in early juveniles. Osteological development is described from a series of cleared and stained specimens. By 14 mm BL all fins have the adult complement of spines and rays. The larvae of A. hololepidotus are briefly compared with those of other Atlantic and Indo-Pacific sciaenids

Black bream in the Blackwood: 2005-06 recreational fishing creel survey

The status of the recreational fishery in the Blackwood Estuary, south-western Australia, was quantitatively assessed via a boat-based creel survey from September 2005 to August 2006. Sampling was stratified by both season and day-type and, in total, was conducted on 144 days over the 12-month period. Daily sampling consisted of a count of number of anglers throughout the estuary (for fishing effort), and surveys of catches by boat-based and shore-based recreational anglers

Shallow-water trawling off the Swartkops Estuary, Algoa Bay

Juvenile fish occurring in Algoa Bay off the mouth of the Swartkops Estuary were collected using a 3-m beam trawl. Pomadasys olivaceum, Engraulis capensis, Caffrogobius agulhensis, Argyrosomus hololepidotus and Galeichthys feliceps were the most abundant species in the trawl catches. Despite the proximity of the Swartkops Estuary, the trawls failed to capture species which are abundant as juveniles in the estuary and it is concluded that the estuary has little influence on the juvenile fish fauna outside the mout

A systematic evaluation of the incremental protection of broad-scale habitats at Ningaloo Reef, Western Australia

Incremental increases to marine conservation areas in response to changing goals, policy, threats or new information are common practice worldwide. Ningaloo Reef, in north-western Australia, is protected by the Ningaloo Marine Park (state waters), which was expanded incrementally in 2004 so that 34% of the park now comprises 'no-take' sanctuary zones. To test the hypothesis that all habitats (benthic cover types) at Ningaloo are actually protected at this 34% level, a systematic conservation planning exercise was conducted using existing broad-scale habitat data (as a surrogate for marine biodiversity) and C-Plan decision-support software. Although subtidal and intertidal coral communities were found to be adequately protected, other habitats, particularly those in deeper waters seaward of the reef, did not attain the 34% target. Efficient incremental additions to the sanctuary zones to allow increased representation of these under-represented habitats were explored with C-Plan. It is recommended that systematic conservation planning incorporating new biodiversity and social information (now becoming available) be undertaken for the next iteration of the Ningaloo Marine Park management plan. This analysis at Ningaloo Reef serves as a useful example of a post hoc systematic approach to guide incremental expansion of existing marine protected areas in other parts of the world

Influence of the Leeuwin Current on the epipelagic euphausiid assemblages of the south-east Indian Ocean

The Leeuwin Current is an anomalous eastern boundary current which transports warm, low salinity water poleward off Western Australia. This study investigated epipelagic euphausiids in the Leeuwin Current system from 22°S to 34°S focusing on the latitudinal gradient in species richness and whether variability in euphausiid assemblages was associated with an increase in seawater density across latitude. Twenty-eight species of euphausiids (including five new records) were identified from the study area. Species richness remained relatively constant across latitude as the distribution of seven tropical species, including the dominant Pseudeuphausia latifrons, extended south of 30°S. Euphausiid assemblages from the northern shelf stations were distinct from the oceanic, shelf break and southern shelf assemblages which, though clustering together, showed evidence of latitudinal shifts and day/night influence, particularly at oceanic stations. Distance-based linear models confirmed that, of the environmental variables examined, mean seawater density was the only significant explanatory variable accounting for 32, 27 and 71% of the variation for shelf, shelf break and night oceanic assemblages, respectively. This study provides the first account of the diversity, distribution and abundance of euphausiids along the entire western seaboard of Australia and enhances understanding of the influence of the Leeuwin Current on holoplanktonic biot

Species Richness, Taxonomic Distinctness and Environmental Influences on Euphausiid Zoogeography in the Indian Ocean

Although two thirds of the world's euphausiid species occur in the Indian Ocean, environmental factors influencing patterns in their diversity across this atypical ocean basin are poorly known. Distribution data for 56 species of euphausiids were extracted from existing literature and, using a geographic information system, spatially-explicit layers of species richness and average taxonomic distinctness (AveTD) were produced for the Indian Ocean. Species richness was high in tropical areas of the southern Indian Ocean (0-20° S), and this high richness extended southwards via the Agulhas and Leeuwin boundary currents. In contrast, the land-locked northern Indian Ocean exhibited lower species richness but higher AveTD, with the presence of the monotypic family Bentheuphausiidae strongly influencing the latter result. Generalised additive modelling incorporating environmental variables averaged over 0-300 m depth indicated that low oxygen concentrations and reduced salinity in the northern Indian Ocean correlated with low species richness. Depth-averaged temperature and surface chlorophyll a concentration were also significant in explaining some of the variation in species richness of euphausiids. Overall, this study has indicated that the patterns in species richness in the Indian Ocean are reflective of its many unusual oceanographic features, and that patterns in AveTD were not particularly informative because of the dominance by the family Euphausiidae

Oceanographic synopsis of the Southern Bluefin Tuna spawning ground in the Eastern Indian Ocean

The only known spawning ground of the Southern Bluefin Tuna (Thunnus maccoyii) occurs in the Eastern Indian Ocean between north-west Australia and Indonesia. This study examined environmental features of this spawning ground using remote sensing and in-situ archived oceanographic data relative to the habitat requirements of the Southern Bluefin Tuna. Environmental data (sea surface temperature, sea level height anomaly, surface chlorophyll a and XBT sections) were extracted from the IMOS portal and used to establish a spatial and temporal oceanographic synopsis Of the area. In addition, CSIRO Atlas of Regional Seas data (CARS; temperature, salinity, oxygen, silicate, nitrate and phosphate) and ARGO data (temperature and salinity) were extracted to supplement the remotely-sensed data. The SST data show significant upwelling (4 degrees Celsius less than the surrounding ocean) along the coastline of Java and Sumatra during the monsoon, about two months before the summer Southern Bluefin Tuna spawning season. This upwelling drives biogeochemical processes that support the pelagic ecosystem in the region. Southern Bluefin Tuna are fast growing; juveniles are voracious predators on macro-zooplankton and small nekton and migrate southwards in the Leeuwin Current to their cool temperate habitat in the Southern Ocean. These fish form the basis of the Port Lincoln tuna ranching industry in South Australia and the longline tuna fishery off New South Wales. It is anticipated that the understanding of the oceanographic features of the spawning ground will provide an important link into the year class strength for this extremely valuable, yet severely depleted, apex fish species