A new nematode species, Buckleyella ornata n. sp. (Philometridae), is described from female speci... more A new nematode species, Buckleyella ornata n. sp. (Philometridae), is described from female specimens found in the abdominal cavity (mesenteries) of the talang queenfish Scomberoides commersonnianus Lacepède (Carangidae, Perciformes) caught in Darwin Harbour, northern Australia. Based on light and scanning electron microscopical examination, the new species mainly differs from the only other congeneric species B. buckleyi Rasheed, 1963 in having a markedly shorter oesophagus (2.04–2.75 mm long), by the absence of a cephalic mound around the mouth aperture, by the presence of four submedian cephalic papillae of the inner circle, and by a somewhat different arrangement of cuticular ornamentations on the body surface. Three protruding oesophageal teeth and large, dome-shaped cephalic papillae of the external circle present in the smallest gravid female of B. ornata are atrophied in larger conspecific gravid females. Buckleyella ornata is the first known nominal species of a philometrid...
Esso Australia Pty Ltd (Esso), in a joint venture with BHP Petroleum Pty Ltd, operates 23 oil and... more Esso Australia Pty Ltd (Esso), in a joint venture with BHP Petroleum Pty Ltd, operates 23 oil and gas production platforms and subsea facilities off the Victorian coast near Gippsland, Australia. The underlying reservoirs have multi-darcy sands and a strong aquifer water drive, so in addition to oil and gas, the extraction activities result in substantial amounts of produced formation water (PFW). Following on-platform treatment, PFW containing a variety of hydrocarbons, ions and inorganics, such as calcium, ammonia, sulfate and trace metals, is discharged into the receiving environment. This paper reports on a study undertaken to investigate the potential effects of PFW discharges from two platforms (Tuna (TNA) and West Kingfish (WKF)) on the receiving environment. Four complementary sampling approaches were used to address the objectives of the study: (1) measure and estimate the dilution of Rhodamine FWT dye solution in the receiving environment following injection into the PFW d...
This study assessed variability in the length and age compositions, longevity, lengthat-age and r... more This study assessed variability in the length and age compositions, longevity, lengthat-age and rates of growth and mortality of the east Australian stout whiting Sillago robusta Stead, 1908 population harvested by demersal trawl fisheries. Sampling was done over 2 years and was spatially stratified across three depth strata between 11 and 90 m at two locations approximately 400 km apart. There were no consistent depth-related differences in length and age compositions, but the mean and median length and age of the population was greater at the lower latitude location. Age classes 2 and 3 years dominated samples in the north, and 1 and 2 years in the south. Observed longevity was 10 years in the north, and 6 years in the south. Mean length-at-age was not consistently different between sexes, years or locations, nor did the von Bertalanffy growth function differ significantly between sexes, even though females had a greater estimated L ∞ (23.45 cm FL) compared to males (22.36 cm FL). Estimated natural mortality (M) ranged between 0.42 and 0.77, using age-and length-based methods. Agebased catch-curve analyses identified the instantaneous rate of total mortality (Z) to range between 1.48 and 2.70, with subsequent estimates of fishing mortality (F) ranging between 1.15 and 2.00, being greater than M. Exploitation rates (E) were greater than 0.7, indicating that S. robusta at the study locations was heavily fished. The data provided here can be used as a basis to evaluate future fishery-and climate-related changes in the population demographics of east Australian S. robusta.
Within the tropics, mangroves and coral reefs represent highly productive biomes. Although these ... more Within the tropics, mangroves and coral reefs represent highly productive biomes. Although these habitats are often within close proximity, the role and importance of mangrove habitats for reef fish species remains unclear. Throughout the Indo-Pacific, reef fish species appear to have few links with estuarine mangrove habitats. In contrast, clear-water non-estuarine mangrove habitats throughout the Caribbean support many reef fish species and may be fundamental for sustaining reef fish populations. But how important are clear-water non-estuarine mangroves for reef fishes within the Indo-Pacific? Using visual surveys during diurnal high tide, the fish assemblages inhabiting clear-water mangrove and adjacent reef habitats of Orpheus Island, Great Barrier Reef, were recorded. Of the 188 species of fishes that were recorded, only 38 were observed to inhabit both habitats. Of these, only eight were observed more than five times within each habitat. These observations provide little indication that the clear-water mangroves are an important habitat for reef fish species. In addition, although based on just a 3-month survey period, we found little evidence to suggest that these areas are important nurseries for reef fish species. The clear-water mangroves of Orpheus Island may, however, provide an additional foraging area for the few reef fish species that were observed to utilize these habitats during high tide. The difference in the importance of clear-water mangroves for reef fishes within this study compared with clear-water mangrove counterparts within the Caribbean is surprising. Although only preliminary, our observations would support suggestions that the patterns reflect the different hydrological characteristics and evolutionary histories of these two biogeographic regions.
Divergent age and growth characteristics can reduce deleterious competitive interactions between ... more Divergent age and growth characteristics can reduce deleterious competitive interactions between taxonomically related species facilitating coexistence. Five platycephalid fish species, Platycephalus caeruleopunctatus, Platycephalus longispinis, Platycephalus richardsoni, Ambiserrula jugosa and Ratabulus diversidens, inhabit inner continental shelf habitats along the east coast of Australia. We tested the hypothesis that the age and growth characteristics of these five species are unique. The age of each species was estimated by counting the number of opaque zones in sectioned otoliths. The maximum observed age ranged from 4 years for A. jugosa to 16 years for P. longispinis. von Bertalanffy growth functions were fitted to length-at-age data for each combination of species, sex and location and compared using likelihood ratio tests. The age and growth characteristics of each species were unique and each species displayed sexually dimorphic growth, with females growing larger than ma...
Knowledge of the life history characteristics of cooccurring species is fundamental to understand... more Knowledge of the life history characteristics of cooccurring species is fundamental to understanding biotic processes that influence structure and maintenance of assemblages of organisms (Schoener 1974, Ross 1986, Roff 1992). Closely related teleost species that coexist often display different life history characteristics, such as reproductive and recruitment strategies, diets and small-scale distributions and abundances (
Artificial reefs have many applications but are best known for their deployments to enhance recre... more Artificial reefs have many applications but are best known for their deployments to enhance recreational fisheries by creating new habitat in areas where natural reef is otherwise limited. The expectation is that fish assemblages will take up residence on artificial reefs and that these assemblages will become at least similar, if not more diverse and abundant, to those on natural reefs. Although designed, purpose-built artificial reefs are becoming more widely used in support of recreational fisheries and many of the historic issues have been resolved, conservation practitioners and managers still face challenges as to the type, number, and arrangement of structures and where to deploy them to maximize benefits and minimize risks. The ecological literature was reviewed to develop and enhance contemporary principles of artificial reef best practices for utilization. Our review identified optimal shapes, vertical relief, void spaces, and unit arrangements for increasing volumes and d...
The dietary composition and partitioning of food resources between five sympatric species of Plat... more The dietary composition and partitioning of food resources between five sympatric species of Platycephalidae inhabiting the coastal waters of New South Wales, Australia was investigated. Samples were collected monthly between March and November 2007 onboard commercial ocean prawn trawlers based in the ports of Yamba and Newcastle. Monthly percentage weight contribution of 12 prey categories was analysed to determine if diet was influenced by the variables: species, location, depth, size and maturity. Of the 959 stomachs from the five species examined, 28-54% contained prey. All Platycephalid species primarily consumed teleosts, however the diversity of prey and the proportion each prey type contributed to the overall diet varied substantially between species. Platycephalus caeruleopunctatus, P. longispinis, P. richardsoni and Ambiserrula jugosa were generalist carnivores and consumed prey from a wide variety of phyla including teleosts, crustaceans, polychaetes, molluscs and echinoderms. In contrast, Ratabulus diversidens were primarily piscivorous. Partitioning of prey resources between species was more evident in waters at Yamba than at Newcastle. Differences in diet between locations were considered a result of differential prey exploitation rather than shifts in the suite of prey consumed. Dietary composition was observed to be influenced by size, maturity status and depth however these differences were not observed for all species.
Journal of the Marine Biological Association of the United Kingdom
The reproductive characteristics of co-occurring freespine flathead, Ratabulus diversidens, and m... more The reproductive characteristics of co-occurring freespine flathead, Ratabulus diversidens, and mud flathead, Ambiserrula jugosa, that interact with fisheries across continental shelf waters of eastern Australia were examined. Samples were collected across three depth strata and two locations on a monthly basis over two years. Males of both species matured younger and at smaller total lengths (TL) than females. Estimated TL and age (years) at maturity (L50 and A50, respectively) of R. diversidens also varied between locations, but differences were not related to differential growth. Although some mature individuals of both species occurred year-round, they were most prevalent and gonadosomatic indices greatest, between the austral spring and autumn. Mature R. diversidens almost exclusively occurred in deeper offshore waters, whereas the opposite was evident for A. jugosa. Both species displayed asynchronous oocyte development, and were thus considered capable of spawning more than o...
Unfortunately, in the original version of the article, the name of the Communicating Editor was p... more Unfortunately, in the original version of the article, the name of the Communicating Editor was published as K. David instead of K. D. Clements.
This study investigated variability in the growth, length, and age compositions and the rates of ... more This study investigated variability in the growth, length, and age compositions and the rates of mortality of Flinders' sillago Sillago flindersi exploited in a demersal trawl fishery in eastern Australia. Sampling was done over 2 years across three depth strata at two locations approximately 400 km apart. Ageing of sectioned sagittal otoliths indicated that the observed maximum age of females was 6 years and that of males 5 years, that growth was variable and that the von Bertalanffy growth parameters significantly differed according to gender and location. Females attained a greater L ? than males, but males displayed greater k values. The L ? values of both sexes and the mean length-at-age for fish aged 3-5 years were greater at the location of highest latitude. Length and age compositions differed according to depth, with smaller (\15 cm FL) and younger (\2 years) fish generally more predominant in the shallow (\30 m) strata than in the deeper ([31 m) strata. S. flindersi appear to use the shallow strata as a juvenile habitat, moving to deeper waters as they grow. This depth stratification between cohorts may reduce intraspecific competition and could potentially be used as a spatial management tool to reduce any fishing-associated impacts on juveniles. Fish between 1 and 3 years old dominated the age compositions of populations combined across all depths, with estimated total mortality ranging between 2.24 and 2.40. Fishing mortality ranged between 1.54 and 1.70 and was more than twice the derived natural mortality. Exploitation rates were approximately 0.70, indicating that the species was heavily fished.
This study investigated variability in the growth, length, and age compositions and the rates of ... more This study investigated variability in the growth, length, and age compositions and the rates of mortality of Flinders' sillago Sillago flindersi exploited in a demersal trawl fishery in eastern Australia. Sampling was done over 2 years across three depth strata at two locations approximately 400 km apart. Ageing of sectioned sagittal otoliths indicated that the observed maximum age of females was 6 years and that of males 5 years, that growth was variable and that the von Bertalanffy growth parameters significantly differed according to gender and location. Females attained a greater L ? than males, but males displayed greater k values. The L ? values of both sexes and the mean length-at-age for fish aged 3-5 years were greater at the location of highest latitude. Length and age compositions differed according to depth, with smaller (\15 cm FL) and younger (\2 years) fish generally more predominant in the shallow (\30 m) strata than in the deeper ([31 m) strata. S. flindersi appear to use the shallow strata as a juvenile habitat, moving to deeper waters as they grow. This depth stratification between cohorts may reduce intraspecific competition and could potentially be used as a spatial management tool to reduce any fishing-associated impacts on juveniles. Fish between 1 and 3 years old dominated the age compositions of populations combined across all depths, with estimated total mortality ranging between 2.24 and 2.40. Fishing mortality ranged between 1.54 and 1.70 and was more than twice the derived natural mortality. Exploitation rates were approximately 0.70, indicating that the species was heavily fished.
This study assessed variability in the length and age compositions, longevity, length-at-age and ... more This study assessed variability in the length and age compositions, longevity, length-at-age and rates of growth and mortality of the east Australian stout whiting Sillago robusta Stead, 1908 population harvested by demersal trawl fisheries. Sampling was done over 2 years and was spatially stratified across three depth strata between 11 and 90 m at two locations approximately 400 km apart. There were no consistent depth-related differences in length and age compositions, but the mean and median length and age of the population was greater at the lower latitude location. Age classes 2 and 3 years dominated samples in the north, and 1 and 2 years in the south. Observed longevity was 10 years in the north, and 6 years in the south. Mean length-at-age was not consistently different between sexes, years or locations, nor did the von Bertalanffy growth function differ significantly between sexes, even though females had a greater estimated L ∞ (23.45 cm FL) compared to males (22.36 cm FL). Estimated natural mortality (M) ranged between 0.42 and 0.77, using age-and length-based methods. Age-based catch-curve analyses identified the instantaneous rate of total mortality (Z) to range between 1.48 and 2.70, with subsequent estimates of fishing mortality (F) ranging between 1.15 and 2.00, being greater than M. Exploitation rates (E) were greater than 0.7, indicating that S. robusta at the study locations was heavily fished. The data provided here can be used as a basis to evaluate future fishery-and climate-related changes in the population demographics of east Australian S. robusta.
More than 65 species of Platycephalidae, commonly known as flathead, are found primarily in the P... more More than 65 species of Platycephalidae, commonly known as flathead, are found primarily in the Pacific and Indian Oceans although some species inhabit the Atlantic Ocean and Mediterranean Sea. Generally flathead are bottom dwellers occurring on soft substrates such as mud, sand and seagrasses across a variety of habitats, ranging from shallow estuaries to deep sea environments. Along the south eastern Australian coastline five species of Platycephalidae; Platycephalus caeruleopunctatus, P. longispinis, P. richardsoni, Ambiserrula jugosa and Ratabulus diversidens coexist within inner-continental shelf habitats. Of these species P. caeruleopunctatus, P. richardsoni and R. diversidens are commercially and recreationally harvested while P. longispinis and A. jugosa are caught and discarded as by-catch. Despite this anthropogenic exploitation, with the exception of P. richardsoni little is known about the biology and ecology of these species. The objectives of this study were to develop...
The dusky flathead (Platycephalus fuscus) is an important teleost harvested by recreational and c... more The dusky flathead (Platycephalus fuscus) is an important teleost harvested by recreational and commercial fishers throughout its endemic distribution along eastern Australia. This study indicates that the species has an extended spawning period throughout the austral summer, with females in spawning condition occurring in lower estuarine and coastal waters. Total length (L50) and age (A50) at which 50% (±1 SE) of the population was mature was 31.72 (±1.08) cm TL and 1.22 (±0.44) years for males and 56.75 (±0.60) cm TL and 4.55 (±0.13) years for females. The von Bertalanffy growth parameters differed significantly between sexes; females grew faster and attained a greater maximum TL and age than males. The largest female was 98.5 cm TL (7.5 kg), and the oldest 16 years, whereas the largest male was 61.5 cm TL (1.58 kg) and 11 years of age. A tag-and-release study identified the exchange of sub-adult and mature-sized individuals among estuaries. Determinations of length-based manageme...
This study investigated variability in the growth, length, and age compositions and the rates of ... more This study investigated variability in the growth, length, and age compositions and the rates of mortality of Flinders’ sillago Sillago flindersi exploited in a demersal trawl fishery in eastern Australia. Sampling was done over 2 years across three depth strata at two locations approximately 400 km apart. Ageing of sectioned sagittal otoliths indicated that the observed maximum age of females was 6 years and that of males 5 years, that growth was variable and that the von Bertalanffy growth parameters significantly differed according to gender and location. Females attained a greater L? than males, but males displayed greater k values. The L? values of both sexes and the mean length-at-age for fish aged 3–5 years were greater at the location of highest latitude. Length and age compositions differed according to depth, with smaller (\15 cm FL) and younger (\2 years) fish generally more predominant in the shallow (\30 m) strata than in the deeper ([31 m) strata. S. flindersi appear to use the shallow strata as a juvenile habitat, moving to deeper waters as they grow. This depth stratification between cohorts may reduce intraspecific competition and could potentially be used as a spatial management tool to reduce any fishing-associated impacts on juveniles. Fish between 1 and 3 years old dominated the age compositions of populations combined across all depths, with estimated total mortality ranging between 2.24 and 2.40. Fishing mortality ranged between 1.54 and 1.70 and was more than twice the derived natural mortality. Exploitation rates were approximately 0.70, indicating that the species was heavily fished.
A new nematode species, Buckleyella ornata n. sp. (Philometridae), is described from female speci... more A new nematode species, Buckleyella ornata n. sp. (Philometridae), is described from female specimens found in the abdominal cavity (mesenteries) of the talang queenfish Scomberoides commersonnianus Lacepède (Carangidae, Perciformes) caught in Darwin Harbour, northern Australia. Based on light and scanning electron microscopical examination, the new species mainly differs from the only other congeneric species B. buckleyi Rasheed, 1963 in having a markedly shorter oesophagus (2.04–2.75 mm long), by the absence of a cephalic mound around the mouth aperture, by the presence of four submedian cephalic papillae of the inner circle, and by a somewhat different arrangement of cuticular ornamentations on the body surface. Three protruding oesophageal teeth and large, dome-shaped cephalic papillae of the external circle present in the smallest gravid female of B. ornata are atrophied in larger conspecific gravid females. Buckleyella ornata is the first known nominal species of a philometrid...
Esso Australia Pty Ltd (Esso), in a joint venture with BHP Petroleum Pty Ltd, operates 23 oil and... more Esso Australia Pty Ltd (Esso), in a joint venture with BHP Petroleum Pty Ltd, operates 23 oil and gas production platforms and subsea facilities off the Victorian coast near Gippsland, Australia. The underlying reservoirs have multi-darcy sands and a strong aquifer water drive, so in addition to oil and gas, the extraction activities result in substantial amounts of produced formation water (PFW). Following on-platform treatment, PFW containing a variety of hydrocarbons, ions and inorganics, such as calcium, ammonia, sulfate and trace metals, is discharged into the receiving environment. This paper reports on a study undertaken to investigate the potential effects of PFW discharges from two platforms (Tuna (TNA) and West Kingfish (WKF)) on the receiving environment. Four complementary sampling approaches were used to address the objectives of the study: (1) measure and estimate the dilution of Rhodamine FWT dye solution in the receiving environment following injection into the PFW d...
This study assessed variability in the length and age compositions, longevity, lengthat-age and r... more This study assessed variability in the length and age compositions, longevity, lengthat-age and rates of growth and mortality of the east Australian stout whiting Sillago robusta Stead, 1908 population harvested by demersal trawl fisheries. Sampling was done over 2 years and was spatially stratified across three depth strata between 11 and 90 m at two locations approximately 400 km apart. There were no consistent depth-related differences in length and age compositions, but the mean and median length and age of the population was greater at the lower latitude location. Age classes 2 and 3 years dominated samples in the north, and 1 and 2 years in the south. Observed longevity was 10 years in the north, and 6 years in the south. Mean length-at-age was not consistently different between sexes, years or locations, nor did the von Bertalanffy growth function differ significantly between sexes, even though females had a greater estimated L ∞ (23.45 cm FL) compared to males (22.36 cm FL). Estimated natural mortality (M) ranged between 0.42 and 0.77, using age-and length-based methods. Agebased catch-curve analyses identified the instantaneous rate of total mortality (Z) to range between 1.48 and 2.70, with subsequent estimates of fishing mortality (F) ranging between 1.15 and 2.00, being greater than M. Exploitation rates (E) were greater than 0.7, indicating that S. robusta at the study locations was heavily fished. The data provided here can be used as a basis to evaluate future fishery-and climate-related changes in the population demographics of east Australian S. robusta.
Within the tropics, mangroves and coral reefs represent highly productive biomes. Although these ... more Within the tropics, mangroves and coral reefs represent highly productive biomes. Although these habitats are often within close proximity, the role and importance of mangrove habitats for reef fish species remains unclear. Throughout the Indo-Pacific, reef fish species appear to have few links with estuarine mangrove habitats. In contrast, clear-water non-estuarine mangrove habitats throughout the Caribbean support many reef fish species and may be fundamental for sustaining reef fish populations. But how important are clear-water non-estuarine mangroves for reef fishes within the Indo-Pacific? Using visual surveys during diurnal high tide, the fish assemblages inhabiting clear-water mangrove and adjacent reef habitats of Orpheus Island, Great Barrier Reef, were recorded. Of the 188 species of fishes that were recorded, only 38 were observed to inhabit both habitats. Of these, only eight were observed more than five times within each habitat. These observations provide little indication that the clear-water mangroves are an important habitat for reef fish species. In addition, although based on just a 3-month survey period, we found little evidence to suggest that these areas are important nurseries for reef fish species. The clear-water mangroves of Orpheus Island may, however, provide an additional foraging area for the few reef fish species that were observed to utilize these habitats during high tide. The difference in the importance of clear-water mangroves for reef fishes within this study compared with clear-water mangrove counterparts within the Caribbean is surprising. Although only preliminary, our observations would support suggestions that the patterns reflect the different hydrological characteristics and evolutionary histories of these two biogeographic regions.
Divergent age and growth characteristics can reduce deleterious competitive interactions between ... more Divergent age and growth characteristics can reduce deleterious competitive interactions between taxonomically related species facilitating coexistence. Five platycephalid fish species, Platycephalus caeruleopunctatus, Platycephalus longispinis, Platycephalus richardsoni, Ambiserrula jugosa and Ratabulus diversidens, inhabit inner continental shelf habitats along the east coast of Australia. We tested the hypothesis that the age and growth characteristics of these five species are unique. The age of each species was estimated by counting the number of opaque zones in sectioned otoliths. The maximum observed age ranged from 4 years for A. jugosa to 16 years for P. longispinis. von Bertalanffy growth functions were fitted to length-at-age data for each combination of species, sex and location and compared using likelihood ratio tests. The age and growth characteristics of each species were unique and each species displayed sexually dimorphic growth, with females growing larger than ma...
Knowledge of the life history characteristics of cooccurring species is fundamental to understand... more Knowledge of the life history characteristics of cooccurring species is fundamental to understanding biotic processes that influence structure and maintenance of assemblages of organisms (Schoener 1974, Ross 1986, Roff 1992). Closely related teleost species that coexist often display different life history characteristics, such as reproductive and recruitment strategies, diets and small-scale distributions and abundances (
Artificial reefs have many applications but are best known for their deployments to enhance recre... more Artificial reefs have many applications but are best known for their deployments to enhance recreational fisheries by creating new habitat in areas where natural reef is otherwise limited. The expectation is that fish assemblages will take up residence on artificial reefs and that these assemblages will become at least similar, if not more diverse and abundant, to those on natural reefs. Although designed, purpose-built artificial reefs are becoming more widely used in support of recreational fisheries and many of the historic issues have been resolved, conservation practitioners and managers still face challenges as to the type, number, and arrangement of structures and where to deploy them to maximize benefits and minimize risks. The ecological literature was reviewed to develop and enhance contemporary principles of artificial reef best practices for utilization. Our review identified optimal shapes, vertical relief, void spaces, and unit arrangements for increasing volumes and d...
The dietary composition and partitioning of food resources between five sympatric species of Plat... more The dietary composition and partitioning of food resources between five sympatric species of Platycephalidae inhabiting the coastal waters of New South Wales, Australia was investigated. Samples were collected monthly between March and November 2007 onboard commercial ocean prawn trawlers based in the ports of Yamba and Newcastle. Monthly percentage weight contribution of 12 prey categories was analysed to determine if diet was influenced by the variables: species, location, depth, size and maturity. Of the 959 stomachs from the five species examined, 28-54% contained prey. All Platycephalid species primarily consumed teleosts, however the diversity of prey and the proportion each prey type contributed to the overall diet varied substantially between species. Platycephalus caeruleopunctatus, P. longispinis, P. richardsoni and Ambiserrula jugosa were generalist carnivores and consumed prey from a wide variety of phyla including teleosts, crustaceans, polychaetes, molluscs and echinoderms. In contrast, Ratabulus diversidens were primarily piscivorous. Partitioning of prey resources between species was more evident in waters at Yamba than at Newcastle. Differences in diet between locations were considered a result of differential prey exploitation rather than shifts in the suite of prey consumed. Dietary composition was observed to be influenced by size, maturity status and depth however these differences were not observed for all species.
Journal of the Marine Biological Association of the United Kingdom
The reproductive characteristics of co-occurring freespine flathead, Ratabulus diversidens, and m... more The reproductive characteristics of co-occurring freespine flathead, Ratabulus diversidens, and mud flathead, Ambiserrula jugosa, that interact with fisheries across continental shelf waters of eastern Australia were examined. Samples were collected across three depth strata and two locations on a monthly basis over two years. Males of both species matured younger and at smaller total lengths (TL) than females. Estimated TL and age (years) at maturity (L50 and A50, respectively) of R. diversidens also varied between locations, but differences were not related to differential growth. Although some mature individuals of both species occurred year-round, they were most prevalent and gonadosomatic indices greatest, between the austral spring and autumn. Mature R. diversidens almost exclusively occurred in deeper offshore waters, whereas the opposite was evident for A. jugosa. Both species displayed asynchronous oocyte development, and were thus considered capable of spawning more than o...
Unfortunately, in the original version of the article, the name of the Communicating Editor was p... more Unfortunately, in the original version of the article, the name of the Communicating Editor was published as K. David instead of K. D. Clements.
This study investigated variability in the growth, length, and age compositions and the rates of ... more This study investigated variability in the growth, length, and age compositions and the rates of mortality of Flinders' sillago Sillago flindersi exploited in a demersal trawl fishery in eastern Australia. Sampling was done over 2 years across three depth strata at two locations approximately 400 km apart. Ageing of sectioned sagittal otoliths indicated that the observed maximum age of females was 6 years and that of males 5 years, that growth was variable and that the von Bertalanffy growth parameters significantly differed according to gender and location. Females attained a greater L ? than males, but males displayed greater k values. The L ? values of both sexes and the mean length-at-age for fish aged 3-5 years were greater at the location of highest latitude. Length and age compositions differed according to depth, with smaller (\15 cm FL) and younger (\2 years) fish generally more predominant in the shallow (\30 m) strata than in the deeper ([31 m) strata. S. flindersi appear to use the shallow strata as a juvenile habitat, moving to deeper waters as they grow. This depth stratification between cohorts may reduce intraspecific competition and could potentially be used as a spatial management tool to reduce any fishing-associated impacts on juveniles. Fish between 1 and 3 years old dominated the age compositions of populations combined across all depths, with estimated total mortality ranging between 2.24 and 2.40. Fishing mortality ranged between 1.54 and 1.70 and was more than twice the derived natural mortality. Exploitation rates were approximately 0.70, indicating that the species was heavily fished.
This study investigated variability in the growth, length, and age compositions and the rates of ... more This study investigated variability in the growth, length, and age compositions and the rates of mortality of Flinders' sillago Sillago flindersi exploited in a demersal trawl fishery in eastern Australia. Sampling was done over 2 years across three depth strata at two locations approximately 400 km apart. Ageing of sectioned sagittal otoliths indicated that the observed maximum age of females was 6 years and that of males 5 years, that growth was variable and that the von Bertalanffy growth parameters significantly differed according to gender and location. Females attained a greater L ? than males, but males displayed greater k values. The L ? values of both sexes and the mean length-at-age for fish aged 3-5 years were greater at the location of highest latitude. Length and age compositions differed according to depth, with smaller (\15 cm FL) and younger (\2 years) fish generally more predominant in the shallow (\30 m) strata than in the deeper ([31 m) strata. S. flindersi appear to use the shallow strata as a juvenile habitat, moving to deeper waters as they grow. This depth stratification between cohorts may reduce intraspecific competition and could potentially be used as a spatial management tool to reduce any fishing-associated impacts on juveniles. Fish between 1 and 3 years old dominated the age compositions of populations combined across all depths, with estimated total mortality ranging between 2.24 and 2.40. Fishing mortality ranged between 1.54 and 1.70 and was more than twice the derived natural mortality. Exploitation rates were approximately 0.70, indicating that the species was heavily fished.
This study assessed variability in the length and age compositions, longevity, length-at-age and ... more This study assessed variability in the length and age compositions, longevity, length-at-age and rates of growth and mortality of the east Australian stout whiting Sillago robusta Stead, 1908 population harvested by demersal trawl fisheries. Sampling was done over 2 years and was spatially stratified across three depth strata between 11 and 90 m at two locations approximately 400 km apart. There were no consistent depth-related differences in length and age compositions, but the mean and median length and age of the population was greater at the lower latitude location. Age classes 2 and 3 years dominated samples in the north, and 1 and 2 years in the south. Observed longevity was 10 years in the north, and 6 years in the south. Mean length-at-age was not consistently different between sexes, years or locations, nor did the von Bertalanffy growth function differ significantly between sexes, even though females had a greater estimated L ∞ (23.45 cm FL) compared to males (22.36 cm FL). Estimated natural mortality (M) ranged between 0.42 and 0.77, using age-and length-based methods. Age-based catch-curve analyses identified the instantaneous rate of total mortality (Z) to range between 1.48 and 2.70, with subsequent estimates of fishing mortality (F) ranging between 1.15 and 2.00, being greater than M. Exploitation rates (E) were greater than 0.7, indicating that S. robusta at the study locations was heavily fished. The data provided here can be used as a basis to evaluate future fishery-and climate-related changes in the population demographics of east Australian S. robusta.
More than 65 species of Platycephalidae, commonly known as flathead, are found primarily in the P... more More than 65 species of Platycephalidae, commonly known as flathead, are found primarily in the Pacific and Indian Oceans although some species inhabit the Atlantic Ocean and Mediterranean Sea. Generally flathead are bottom dwellers occurring on soft substrates such as mud, sand and seagrasses across a variety of habitats, ranging from shallow estuaries to deep sea environments. Along the south eastern Australian coastline five species of Platycephalidae; Platycephalus caeruleopunctatus, P. longispinis, P. richardsoni, Ambiserrula jugosa and Ratabulus diversidens coexist within inner-continental shelf habitats. Of these species P. caeruleopunctatus, P. richardsoni and R. diversidens are commercially and recreationally harvested while P. longispinis and A. jugosa are caught and discarded as by-catch. Despite this anthropogenic exploitation, with the exception of P. richardsoni little is known about the biology and ecology of these species. The objectives of this study were to develop...
The dusky flathead (Platycephalus fuscus) is an important teleost harvested by recreational and c... more The dusky flathead (Platycephalus fuscus) is an important teleost harvested by recreational and commercial fishers throughout its endemic distribution along eastern Australia. This study indicates that the species has an extended spawning period throughout the austral summer, with females in spawning condition occurring in lower estuarine and coastal waters. Total length (L50) and age (A50) at which 50% (±1 SE) of the population was mature was 31.72 (±1.08) cm TL and 1.22 (±0.44) years for males and 56.75 (±0.60) cm TL and 4.55 (±0.13) years for females. The von Bertalanffy growth parameters differed significantly between sexes; females grew faster and attained a greater maximum TL and age than males. The largest female was 98.5 cm TL (7.5 kg), and the oldest 16 years, whereas the largest male was 61.5 cm TL (1.58 kg) and 11 years of age. A tag-and-release study identified the exchange of sub-adult and mature-sized individuals among estuaries. Determinations of length-based manageme...
This study investigated variability in the growth, length, and age compositions and the rates of ... more This study investigated variability in the growth, length, and age compositions and the rates of mortality of Flinders’ sillago Sillago flindersi exploited in a demersal trawl fishery in eastern Australia. Sampling was done over 2 years across three depth strata at two locations approximately 400 km apart. Ageing of sectioned sagittal otoliths indicated that the observed maximum age of females was 6 years and that of males 5 years, that growth was variable and that the von Bertalanffy growth parameters significantly differed according to gender and location. Females attained a greater L? than males, but males displayed greater k values. The L? values of both sexes and the mean length-at-age for fish aged 3–5 years were greater at the location of highest latitude. Length and age compositions differed according to depth, with smaller (\15 cm FL) and younger (\2 years) fish generally more predominant in the shallow (\30 m) strata than in the deeper ([31 m) strata. S. flindersi appear to use the shallow strata as a juvenile habitat, moving to deeper waters as they grow. This depth stratification between cohorts may reduce intraspecific competition and could potentially be used as a spatial management tool to reduce any fishing-associated impacts on juveniles. Fish between 1 and 3 years old dominated the age compositions of populations combined across all depths, with estimated total mortality ranging between 2.24 and 2.40. Fishing mortality ranged between 1.54 and 1.70 and was more than twice the derived natural mortality. Exploitation rates were approximately 0.70, indicating that the species was heavily fished.
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