bluuebunny/crossref_metadata_2025 huggingface dataset:
Estuarine Ichthyoplankton Ecology in Relation to Hydrology and Zooplankton Dynamics in salt-wedge Estuary
Authors: Newton GM
Published: November 2005

The ichthyoplankton assemblage of the Hopkins River estuary, Victoria, was dominated by estuarine taxa that included demersal (goby, gudgeon) and pelagic (black bream, estuary perch, anchovy) species. The two seasonal peaks in fish larvae abundance were related to (1) the spring/summer zooplankton increase that occurred after flooding of the estuary and was comprised predominantly of copepod nauplii, thereby providing a good prey field for very young fish larvae, and (2) the autumn zooplankton maxima, which would provide a wide selection of copepod stages and meroplankton and promote dietary partitioning and flexibility among older larval stages. The two peaks in fish larvae abundance occurred well before and well after the attainment of maximum water temperature in the estuary. Goby, gudgeon, estuary perch and anchovy larvae were in the plankton over an extended period coinciding with the more stable conditions of salt-wedge presence and maximum zooplankton densities. The spawning of black bream and anchovies in the estuary was clearly related to physical conditions, such as salinity and water temperature, and habitat-although spawning of both species also occurred at times of high concentrations of potential prey organisms for their larvae. Adults of all the above fish species appear to have evolved spawning strategies that are adapted to the average hydrological and biological conditions in the estuary that would lead to the enhanced survival of their larvae. With the exception of the black bream, it appears that a ubiquitous and prolonged rather than a synchronous and confined spawning strategy is more widely used by estuarine-spawning fishes in the Hopkins River estuary. This type of spawning strategy, combined with the generally high density of food available to fish larvae in estuaries, suggests that the match-mismatch hypothesis of Cushing may be less relevant in the estuarine than in the marine environment.
A Bioenergetic Exploration of Piscivory and Planktivory During the early Life History of Two Species of Freshwater Fishes.
Authors: Werner RG , Jonckheere BV , Clapsadl MD , Farrell JM
Published: November 2005

In order to explore the trophic relationships of two different feeding strategies during the nursery period a bioenergetic model is applied to the early life history stages of a piscivore, the muskellunge (Esox masquinongy, Esocidae: Salmoniformes) and a planktivore, the bluegill (Lepomis macrochirus, Centrarchidae:Perciformes). The model uses a balanced energy equation to predict consumption based on observed growth and calculated losses to metabolism, excretion and egestion. Estimates are temperature- and weight-dependent and are calculated on a daily basis over the duration of the nursery period. Ambient temperatures and the diet composition as determined from stomach content analysis were used in the model. Comparisons of consumption and metabolic rates between a piscivore and a planktivore suggest that the planktivore has a much higher metabolic rate resulting in greater weight-specific consumption and a larger maximum ration (g g-1 day-1 day-1) than the piscivore. The consumption of prey organisms in relation to prey standing crop by the planktivore ranged up to 2.5% of the standing crop per day, whereas in the piscivore population it approached 18% of standing crop per day; this suggests that consumption by the planktivore on the zooplankton population in eutrophic Crane Lake would likely have less of an effect on the prey population than that of the piscivore in bays of the St Lawrence River.
Is Ichthyoplankton Predation an Important Source of Copepod Mortality in Subtropical Coastal Waters?
Authors: Dagg MJ , Govoni JJ
Published: November 2005

The significance of ichthyoplankton-induced mortality to copepods was examined at three localities in the northern Gulf of Mexico: in the winter at a site of an exceptionally high concentration of larval spot, Leiostomus xanthurus; in the winter at a highly productive region near the Mississippi River delta; and in the summer in a highly eutrophic estuary dominated by larval bay anchovy, Anchoa mitchilli. In each region, ichthyoplankton ingestion of copepod eggs, nauplii and copepodids was compared with production rates and stocks of the dominant copepod species in the same waters. In all cases, predation from the dominant larval species and from the total ichthyoplankton assemblage was much less than prey production. It is concluded that ichthyoplankton predation in these regions rarely has any significant effect on copepod population dynamics, and therefore larval competition for food is unlikely to contribute to density-dependent mortality.
Effect of the Leeuwin Current on the Recruitment of Fish and Invertebrates along the Western Australian Coast
Authors: Caputi N , Fletcher WJ , Pearce A , Chubb CF
Published: November 2005

The relatively high catch of invertebrate species compared with finfish off Western Australia is in sharp contrast to other regions of the world, where finfish production usually dominates. This low level of finfish production is primarily due to the Leeuwin Current, which consists of warm, low-nutrient waters flowing south along the edge of the continental shelf of the Western Australian coast. In contrast, the other eastern boundary currents in the Southern Hemisphere (Humboldt and Benguela) are associated with upwelling of cool, nutrient-rich waters flowing north and the high rates of primary production resulting in a large finfish production. The Leeuwin Current, being the dominant oceanographic feature off Western Australia, has a major influence on the abundance of many species. The larval phase is the stage mainly affected by the current, but not always with the same result. For example, the strength of the Leeuwin Current has a significant positive influence during the larval stage of the western rock lobster (Panulirus cygnus). However, the current has a negative influence during the larval life of the scallop, Amusium balloti, in Shark Bay. Similarly for the pelagic finfish species, the current has a negative effect on larval survival of pilchards (Sardinops sagax neopilchardus) but a positive impact for whitebait (Hyperlophus vittatus). Possible mechanisms for the effect of the current include transportation of larvae and temperature effects on spawning success and on survival and growth of larvae.
How do Riverine Plumes of Different Sizes Influence Fish Larvae: do they Enhance Recruitment?
Authors: Grimes CB , Kingsford MJ
Published: November 2005

A review of the literature suggests that river discharge plumes strongly influence fish larvae and may play a significant role in the recruitment of local fishes. Some rivers drain large land masses to discharge shallow, turbid and nutrient-rich plumes that interact with ocean currents as well as with local oceanography and meteorology; these plumes may extend hundreds of kilometres offshore and alongshore. The frontal, or mixing, zone between plume and ocean waters is characterized by strong physical and biological processes. Physical dynamics, e.g. hydrodynamic convergence, and abundant nutrients (both river derived and upwelled) in the vicinity of discharge plumes often generate large stocks of phytoplankton, zooplankton and fish larvae, as well as high rates of primary and secondary production. Physical dynamics not only act to accumulate (and probably retain) biomass in frontal waters, but also transport organisms onshore, offshore and along the frontal boundary.
The mechanisms through which river plumes may influence recruitment are not clear. In considering the potential effects of scale of river discharge on recruitment, three alternative hypotheses are discussed. The short-food-chain hypothesis states that recruitment will be enhanced in the vicinity of river plumes because fish larvae experience superior feeding conditions, grow faster and thus experience a shorter stage duration and survive better. The total-larval-production hypothesis is that trophic conditions support such high total production of fish larvae that specific dynamics of growth and mortality are not relevant. The third hypothesis is that plumes facilitate the retention of fish larvae within a limited area, and it is the physical retention rather than production that explains the variation in recruitment. If one or a combination of these hypotheses explains the influence of river plumes on recruitment, then the greatest potential to affect fish recruitment may be possessed by large mid-latitude rivers carrying high suspended-sediment and nutrient loads that discharge into shelf waters to create well defined plumes where primary and secondary production are high.
Culture technology of marine rotifers and the implications for intensive culture of marine fish in Japan
Authors: Yoshimura K , Hagiwara A , Yoshimatsu T , Kitajima C
Published: November 2005

In order to expand the practice of rearing marine finfish larvae, it is necessary to increase and stabilize the production of live feed. Latest researches on rotifer culture technology in Japan have aimed at these objectives. This paper summarizes the progress on the technology of high-density rotifer mass cultures. The high-density culture of the marine rotifer Brachionus rotundiformis (so-called S-type) enables production that is at least 100 times more efficient than that by the conventional method, with less cost for production. The technology is based on the use of highly concentrated algal biomass as food for rotifers. Rotifers are mass-cultured at 10000-30000 individuals mL-1 by feeding them exclusively on condensed freshwater Chlorella. Cultures are generally supplied with constant O2; pH is adjusted to 7 by addition of HCI to avoid an increase of free ammonia in the culture system. The excess suspended organic matter can be efficiently removed by a nylon filtration mat.
Rearing Halibut in Norway: Present Practices and Challenges
Authors: Pittman K
Published: November 2005

Atlantic halibut (Hippoglossus hippoglossus L.) has been identified as the species that can best complement the salmon farming industry in Norway. From an experimental fry production of only 2 in 1985 to a production of over 350000 in 1994 and commercial sales of 60 t in 1995, the advances have accumulated through close cooperation between research and industry. Current practices involve holding the broodstock on natural or controlled photoperiod, stripping and disinfecting eggs before incubation in darkness, controlling larval placement in the water column, and first-feeding on natural zooplankton in green water. Many of the original practices are being examined with a critical eye, such as use of salt during removal of bottom water and the necessity of maintaining the larvae in darkness beyond 150 degree-days. Early temperature regimes play a role in viability, and experimental evidence points to changing temperature optima with size and to effects of light and photoperiod on growth, behaviour and survival in most stages. Challenges include identification of the period in which pigmentation is affected by exogenous nutrients, control and synchronization of metamorphosis, early identification and separation of the fast-growing females in the populations, and prevention of the early maturation in males. These and other biological and environmental requirements of the developing halibut must be better understood to achieve predictable production routines.
Incidence and Composition of Calculi in the Urinary Bladder of Intensively Reared Marine Fish Larvae
Authors: Nowak BF , Battaglene SC
Published: November 2005

Calculi were observed in the urinary tracts of a wide range of intensively reared marine fish larvae at the Port Stephens Research Centre. Data are presented for three species: snapper Pagrus auratus, mulloway Argyrosomus hololepidotus, and Australian bass Macquaria novemaculeata. Calculi first appeared in P. auratus on Day 5 after hatching, in M. novemaculeata on Day 11, and in A. hololepidotus on Day 12. Around 80% of larvae typically had calculi after two weeks of intensive rearing. No relationship could be found between the absence of the functional swim bladder and the presence of calculi in all species studied. The presence of calculi did not stop the larvae of any species from actively feeding on live prey. Calculi from M. novemaculeata and P. auratus were analysed with an electron probe microanalyser. Phosphorus and calcium were detected in all calculi, usually accompanied by magnesium. Potential causes for the formation of calculi are discussed.
Preliminary Observations on Development of Pacific Bluefin Tuna Thunnus thynnus (Scombridae) Larvae Reared in the Laboratory, with Special Reference to the Digestive System
Authors: Kaji T , Tanaka M , Takahashi Y , Oka M , Ishibashi N
Published: November 2005

Pacific bluefin tuna larvae (Thunnus thynnus) were experimentally reared from 2-day-old yolk-sac larvae through 30-day-old early juveniles in June and July 1994. The larvae initially fed on rotifers on Day 3 and Artemia nauplii, fish eggs and larvae around Day 13, and thereafter were fed Artemia larvae and an artificial diet. The larvae had transformed to the juvenile stage after 30 days. The primitive digestive system differentiated on Day 3. The gastric gland and pyloric caeca first appeared on Day 11 and 14, respectively. The pharyngeal and jaw teeth became fully functional with gastric gland differentiation. The number of gastric glands and pyloric caeca and volume of the gastric blind sac increased markedly with development to the juvenile stage. Although the external morphological development of the tuna resembles the pattern of many other marine fish larvae, the basic digestive system developed at an earlier larval stage; this precocity may relate to the early appearance of piscivory and the high growth potential of tuna larvae.
Relative RNA Content as a Measure of Condition in Larval and Juvenile Fish
Authors: Suthers IM , Cleary JJ , Battaglene SC , Evans R
Published: November 2005

The RNA:DNA ratio for first-feeding larvae (12 days after hatching, 4-6 mm standard length, SL) of Australian bass (Percichthyidae, Macquaria novemaculeata) exposed to four different feeding regimes over 8 days was found to be insensitive to the level of starvation. An alternative condition index based on residuals derived from the regression of RNA on SL showed significant differences over the course of the experiment; these reflected the four feeding treatments. Field collections of juvenile monacanthids (Paramonacanthus otisensis, 10-30 mm SL) from a local estuary revealed no significant difference in RNA: DNA ratio at three sites over six weeks. A residual-based index (RNA on dry weight) showed parallel fluctuations at all sites; they were positively correlated with water temperature. The RNA : DNA ratio depends on the difference in fluorescence between total nucleic acids (TNA, using thiazole orange) and DNA (using Hoechst 33258) to calculate RNA, as there is no RNA-specific fluorescent dye. The numerator is thus dependent on the denominator, and measurement error may be compounded in the ratio, exacerbating potential variability in the index. Ratios may also be variably correlated with age or size and consequently may erroneously indicate condition or growth in larger and faster-growing fish.
Distribution of Bluefish (Pomatomus saltatrix) Larvae along the Continental Shelf off Southern Brazil
Authors: Muelbert JH , Sinque C
Published: November 2005

Data from ichthyoplankton surveys between 1980 and 1990 are used to describe the distribution of bluefish (Pomatomus saltatrix) larvae along the continental shelf off southern Brazil (24�-35�S). Only 46 larvae in 9 stations were found in 1026 oblique and horizontal tows taken with a 330 pm-mesh Bongo net. Larvae ranged in size from 3 to 10 mm, with the larger larvae distributed close to shore. There were no significant differences in size between larvae found in the northern and southern regions of the shelf. However, there was evidence of a gradual northward displacement of larval abundance towards winter. About 85% of the larvae occurred in the southernmost region of the shelf (below 32�S) in January and February (summer), and the remaining larvae were caught further north from March to August. This pattern of larval distribution could be attributed to the northwards retreat of warmer (> 20�C) and more saline (> 34) Brazilian coastal waters from the region. Results from this study suggest that bluefish spawn over a protracted period, following the seasonal displacement of Brazilian coastal waters along the continental shelf off southern Brazil, a pattern that is also consistent with the spawning migration proposed for bluefish in the north-western Atlantic.
Early Life History of Pomatomus saltatrix off the East Coast of South Africa
Authors: Beckley LE , Connell AD
Published: November 2005

Several authors have stated that southward transport of the early life-history stages of Pomatomus saltatrix occurs by passive drift in the Agulhas Current, a strong western boundary current which flows southwards following the edge of the continental shelf of eastern South Africa. However, an extensive study of the ichthyoplankton occurring in shelf and Agulhas Current waters from 29�S to 34�S located P. saltatrix larvae only in the shelf waters off KwaZulu-Natal. Sampling of fish eggs in the inshore shelf waters 60 km south of Durban on a regular basis has confirmed spawning of P. saltatrix to occur in this region. The data thus suggest that larval dispersal might occur in shelf waters where, although strongly influenced by the Agulhas Current, southward transport is not as rapid.
Comparing Early Life History Strategies of Pomatomus saltatrix: a Global Approach
Authors: Juanes F , Hare JA , Miskiewicz AG
Published: November 2005

Pomatomus saltatrix (Pisces:Pomatomidae) is a highly migratory, continental-shelf species with a worldwide subtropical distribution including the eastern coast of North America, the Gulf of Mexico, Mediterranean Sea, Black Sea, north-western Africa, the eastern coast of South America, the south-eastern coast of South Africa, and the south-eastern and south-westem coasts of Australia. This paper summarizes available life history information from the different regions where P. saltatrix occurs, with a focus on the early life history. The basic physical oceanography of these regions is also reviewed to elucidate patterns in larval transport. Comparison of these populations suggests that there are commonalties: adults migrate to spawning grounds; eggs and larvae are typically advected along-shore to juvenile nursery habitats; juveniles recruit to inshore habitats at a similar size, and there they grow rapidly and are mainly piscivorous, feeding primarily on atherinids and engraulids. There are also a number of life history traits that are quite variable among populations: the number of annual reproductive peaks, the number of juvenile cohorts, adult growth patterns and reproductive parameters. Comparison of these life history patterns leads to several non-exclusive hypotheses as to the adaptive significance of variations in life history traits. The goal is to identify areas where more research is needed to assess the degree to which populations of a global species are adapted to their local environment.
Habitat Selection before Settlement by Pomacentrus coelestis
Authors: Doherty P , Kingsford M , Booth D , Carleton J
Published: November 2005

The neon damsel, Pomacentrus coelestis, is characteristic of surge zones on Australian coral reefs and is most abundant on outer slopes of reefs in the southern Great Barrier Reef. When settling, it appears to 'avoid' lagoonal habitats. Recruitment records confirm that this is a general pattern regardless of whether lagoons have permanent or temporary connections to the ocean. This study included direct sampling, around One Tree Reef from the southern Great Barrier Reef, of all presettlement stages of P. coelestis with the aid of light-traps, channel nets and a plankton purse seine. Pelagic juveniles were abundant in catches from light-traps moored outside of the reef crest. In contrast, this developmental stage was rare in catches from all gear types used within the lagoon. The channel nets collected newly hatched larvae that entered the lagoon at night, but either they did not remain in the lagoon or they did not survive because they were not taken from the lagoon by diurnal purse seines. This direct evidence shows that broad-scale habitat selection can begin in the planktonic stage. It implies that pelagic juveniles have excellent sensory and motor capabilities, which disqualify them from being classified and modelled as plankton. Temperature records from inside and outside of the lagoon indicated that warm plumes (up to 3�C above ambient) influence reef waters near One Tree Reef, and temperature may be one of the cues that presettlement fish use to identify lagoonal habitats.
What the Pelagic Stages of Coral Reef Fishes Are Doing out in Blue Water: Daytime Field Observations of Larval Behavioural Capabilities
Authors: Leis JM , Sweatman HPA , Reader SE
Published: November 2005

Late pelagic stages of coral reef fishes captured with light-traps were individually released during daylight by SCUBA divers in open water, 20-35 m deep, in the Great Barrier Reef Lagoon at three sites > 1 km from the reefs of Lizard Island. Observations in situ on 111 individuals of 11 families, but primarily Apogonidae, Chaetodontidae and Pomacentridae, constitute the first data of their kind. Most fish showed no overt reaction to the divers. Some individuals of some taxa of three families settled quickly to the bottom. Acceptable observations on swimming were made on 66 larvae. Individuals selected a wide range of depths, but when grouped by family, mean depths chosen by individuals were: apogonids, 6.5 (� 1.5, 95% CI) m; pomacentrids, 7.7 (� 1.5) m; and chaetodontids, 9.3 (� 1.3) m. Rough estimates of speed of up to 30 cm s-1 varied among taxa. Swimming directions of 59 of the 66 larvae were non-random. Mean directions differed among sites and were offshore at all of them. Most larvae swam offshore regardless of the side of the island where they were released. The late pelagic stages of coral reef fishes are strong swimmers capable of active horizontal and vertical movement. They swim directionally, can apparently detect reefs >1 km away, and orientate relative to those reefs. A taxonomic component is evident in many of these behaviours.
Larval Supply and Patterns of Recruitment for Two Caribbean Reef fishes Stegastes partitrus
Authors: Sponaugle S , Cowen RK
Published: November 2005

To examine the relative roles of physical and biological processes involved in the recruitment of reef fishes, temporal and spatial patterns of supply and recruitment were measured for two fishes, Stegastes partitus (Poey) (Pomacentridae) and Acanthurus bahianus Castelnau (Acanthuridae), recruiting to Barbados, West Indies. Nightly light-trap collections of late-stage larvae were compared with patterns of juvenile recruitment. Otolith records provided estimates of larval duration and post- settlement age. Temporal patterns of larval supply were similar for both species: abundances peaked during the third-quarter moon. However, spatial patterns of larval supply varied between species: during large recruitment events, S. partitus larvae were more abundant in the south, A. bahianus in the north, suggesting that larval supply was not simply the result of passive transport. Patterns of supply were subsequently maintained (S. partitus) or modified (A. bahianus) by juveniles. In general, densities of juvenile S. partitus were evenly distributed along the coast; however, during major events, spatial patterns of recruitment reflected patterns of larval supply. In contrast, densities of juvenile A. bahianus were directly opposite patterns of larval supply, suggesting that for some species, postsettlement processes such as habitat selection may be more influential in creating spatial patterns of recruitment.
Local-scale Patterns of Larval Settlement in a Planktivorous Damselfish—Do They Predict Recruitment?
Authors: Schmitt RJ , Holbrook SJ
Published: November 2005

The degree to which local-scale spatial variation in larval supply predicted subsequent patterns in juvenile densities was examined for a planktivorous damselfish (Dascyllus trimaculatus) at Moorea, French Polynesia. D. trimaculatus young settle from the plankton to sea anemones, where they remain until becoming free-ranging adults. Daily settlement onto anemones without fish was estimated at several sites in a lagoon for one 14-day period and compared with patterns in the density of juveniles that had accrued after 10 successive settlement periods. Spatial variation attributable to larval supply occurred mostly among individual anemones, between the halves of each study site, and among different locations in the lagoon. In contrast, there was relatively little variation at any spatial scale in the density of young after 10 settlement pulses. Several mechanisms were examined that could account for the observed reduction in spatial variance through time, and three involving interactions with young already present were implicated. First, settlement was not independent of residents (the density of young already on an anemone); compared with the absence of fish, settlement was facilitated at low and inhibited at high densities of residents. Second, older juveniles moved among local anemones, and the immigration and emigration rates per capita varied with density on an anemone. Finally, per capita mortality during the first few days after settlement was density-dependent. These findings emphasize the critical need to distinguish among effects that arise from the delivery of larvae, the availability of appropriate habitat, and interactions that affect fish at settlement and immediately thereafter.
The Leeuwin Current near Rottnest Island, Western Australia
Authors: Cresswell G
Published: November 2005

Ship data and a satellite image in June 1987 showed the Leeuwin Current as a warm, low-salinity tropical stream travelling southward inshore of the 180-m isobath with near-surface speeds up to 0.9 m s-1. Farther offshore, where the waters became progressively more subtropical, the southward currents were also quite strong--0.75 m s-1 above the continental slope and over 0.4 m s-1 out to 70 km beyond the shelf edge. Beyond this, a doming of 150 m in the temperature structure at several hundred metres depth drove a cyclonic eddy that had its maximum speed of ~0.5 m s-1 in a ring at 200-400 m depth. The presence of the eddy was confirmed by the path of a drifter. Geostrophic currents and currents measured directly with an Acoustic Doppler Current Profiler showed good agreement. The warm 'shoulder' of the Leeuwin Current between the 105-m and 135-m isobaths was a biological oasis characterized by, inter alia, several fish schools at least 10 km long and 1 km wide and with vertical extents from 20 m to more than 100 m depth.
Mesoscale variability in volume transport in the Tasman and Coral Seas
Authors: Hamilton LJ
Published: November 2005

Mesoscale variability of volume transports for the upper 450 m of the south-west Pacific is examined with repeat expendable bathythermograph temperature cross-sections, using a level of no motion of 1300 m. Salinity and dynamic heights are synthesized. The 136 sections are clustered about seven particular routes between Australia, Fiji and New Zealand. Peak values of net transports across one- degree latitude or longitude bins along routes are found to be an effective method of defining spatial variability, reflecting current features quite strongly. Higher local transports are indicated along the flanks of Lord Howe Rise, West Norfolk Ridge and parts of Challenger Plateau, emphasizing the topographically controlled nature of the currents. Little seasonality is evident. A very broad mean transport pattern is consistent with results in the literature derived by other methods, as are transports for the East Australian Current, indicating that results are representative. The reliability of the mean pattern is examined in terms of directional persistence, e.g. net outflows to the east are strongly directional north and north-west of New Zealand. Error calculations and an overall regularity of results indicate a valid analysis.
Trace elements in the otoliths of New Zealand blue grenadier (Macruronus novaezelandiae) as an aid to stock discrimination
Authors: Kalish JM , Livingston ME , Schofield KA
Published: November 2005

Blue grenadier, Macruronus novaezelandiae, or hoki as it is known in New Zealand, spawns at two distinct localities off New Zealand. Earlier research on morphometrics and on age and growth suggested that these spawning localities are used by two discrete stocks; however, the research was not conclusive. Inductively coupled plasma-atomic emission spectroscopy (ICP-AES) was used to analyse trace elements in otoliths from adult blue grenadier collected at the two spawning sites. Before analysis, portions of otoliths formed during juvenile and adult life were isolated and these segments were analysed separately. With a cross-validation procedure (jackknife), it was possible to classify correctly 100% of the samples in relation to age (juvenile v. adult). On the basis of the jackknifed discriminant functions, classifications of blue grenadier in relation to sex or capture locality were not significantly different from random. The results are not definitive in determining stock structure of New Zealand blue grenadier but do provide insight into the application of otolith trace element chemistry in studies of stock structure.
Predation and its influence on the condition of a newly settled tropical demersal fish
Authors: McCormick MI , Kerrigan BA
Published: November 2005

The effects of predation by a common tropical piscivore on levels of variability in size and body composition of a demersal fish at settlement were examined in a series of laboratory experiments. Wild-caught, newly metamorphosed goatfish (Upeneus tragula) were placed in large tanks and subjected to predation by lizardfish (Synodus variegatus). Three trials failed to show an influence of predation on the size distribution of the newly settled prey. In a second experiment, mid-larval-phase goatfish were subjected to one of two feeding regimes; this resulted in two groups of metamorphs that differed markedly in biochemical composition (i.e. total lipid levels). Twenty fish from each treatment were randomly chosen, under the constraint of a similar mean size, and subjected to predation. Susceptibility of newly metamorphosed fish to predation by the lizardfish was independent of their initial biochemical composition. These results suggest that predation by this common tropical reef fish predator may be non-selective with respect to both size and body composition of U. tragula. Consequently, the high variability found in these body attributes at settlement may extend its influence into the juvenile population.
Species richness and geographical variation in assemblage structure of the freshwater fish fauna of the wet tropics region of northern Queensland
Authors: Pusey BJ , Kennard MJ
Published: November 2005

A field survey of the freshwater piscifauna of the Wet Tropics region of northern Queensland was undertaken in August, September and October 1993. Sixty-six species of fishes, only two of which were exotic, were collected during the study, and reference to a further 12 species was found in the literature. The region contains two-thirds of the continent's fish genera and 40% of species. If the comparison is restricted to only those genera and species found in northern Australia, then the proportions increase to 80% and 55% respectively. Several species not previously recorded from Australia and one undescribed species from the family Percichthyidae, were collected. Ordination of the data set revealed a strong latitudinal gradient in assemblage structure, with the Bloomfield River and streams of the Cape Tribulation area and the Cardwell area containing the most distinctive faunas. The remaining seven drainages formed a homogenous group with little inter-basin separation, probably because they share similar hydrologies, water quality and contain a similar array of habitats. Discontinuities in river profile had a marked effect on assemblage structure.
Spatial and temporal variation in populations and community of ectoparasites on young snapper, Pagrus auratus (Bloch & Schneider) (Sparidae), from the wild and captivity at Port Hacking, Sydney, Australia
Authors: Roubal FR , Quartararo N , West A
Published: November 2005

Snapper in both the estuary (0+, 1+ age classes) and from offshore reefs (1+, 2+, 3+ age classes) at Port Hacking, NSW, were infested with the monogeneans Lamellodiscus pagrosomi, Anoplodiscus cirrusspiralis and Bivagina pagrosomi and the copepods Unicolax chrysophryerzus, Pseudoeucanthus australiensis, Hatschekia pagrosomi, Clavellopsis sargi and Lernanthropus atrox; offshore snapper also had the monogenean Choricotyle australiensis and the copepods Caligus spp. and Lepeophtheirus sekii. Most species had a higher prevalence, but not intensity, on offshore fish. Season was not a significant factor for most infrapopulations. Species richness, number of parasites and diversity were greater on offshore fish and differed among estuary samples but not offshore samples. Estuary infracommunities were dominated by L. pagrosomi (mainly 1+) and B. pagrosomi (mainly 0+); C. sargi and L. atrox dominated when richness was low. Offshore infracommunities were dominated by H. pagrosomi except in winter when L. pagrosomi was dominant, possibly owing to movement of estuary fish to offshore reefs. Captivity in experimental cages in the estuary resulted in transient increases in A. cirrusspiralis, B. pagrosomi and Benedenia sekii. Lamellodiscus pagrosomi increasingly dominated all samples and infracommunities. Neither condition factor nor stocking density had a significant influence on infestation.
Copepod egg production and food resources in Exmouth Gulf, Western Australia
Authors: McKinnon AD , Ayukai T
Published: November 2005

Measurements of plankton community structure, copepod egg production and potential
copepod trophic resources were made in Exmouth Gulf, north-westem Australia. Egg production rates
by four of the dominant copepod species-Acartia fossae, Parvocalanus crassirostris, Oithona
attenuata and O. simplex-were measured by bottle incubations and the egg-ratio technique. Plankton
abundance and biomass did not differ greatly within the gulf; however, highest values of chlorophyll a,
particulate carbon and nitrogen, and copepod egg production rates occurred in the south-east of the gulf.
Though egg production rates were low and apparently severely food-limited, resuspension of bottom
sediments or export of material from adjacent salt flats may fuel production in shallow inshore areas of
the gulf. P. crassirostris appeared to be omnivorous and O. attenuata primarily herbivorous, but the
trophic resources used by O. simplex and A. fossae could not be identified. From the egg production data,
it was calculated that adult females of the four dominant copepod species graze 12% of the total
particulate carbon each day.
Density, biomass and species composition of fish in a subtropical Rhizophora stylosa mangrove forest
Authors: Halliday IA , Young WR
Published: November 2005

Juvenile and adult fish were sampled from within a subtropical Rhizophora stylosa mangrove forest in Tin Can Bay, Australia, every second lunar month from November 1991 to November 1993. On all sampling occasions replicate samples were taken on two consecutive nights. In all, 3320 fish were collected, representing 42 species and weighing 141 498 g. Significantly fewer fish were caught on the second night than on the first night. Economically important fish of the Families Atherinidae, Mugilidae, Gerreidae, Sparidae and Sillaginidae represented >76% by number and >74% of the total weight caught. The mean density of fish in the forest was 0.04 � 0.01 m-2, with a biomass of 1.3 � 0.2 g m-2. This is lower than that found in similar studies on other mangrove communities. The fish community was dominated by detritivores and intermediate carnivores, many of which are of economic value. Although the fish use of this subtropical R. stylosa forest was low, this habitat is important as a feeding and nursery area for fish species that contribute to the fisheries value of the region.
Sea snake by-catch of fish trawlers on the northern Australian continental shelf
Authors: Ward TM
Published: November 2005

During 1986-90, 206 sea snakes were collected from Taiwanese pair-trawlers (North West Shelf, 1986-87), Thai stern-trawlers (Arafura Sea, 1986-87), RV Soela (North West Shelf, 1986) and RV Clipper Bird (Timor and Arafura Seas, 1990). Taiwanese (58 specimens; 294.8 h trawled) and Thai (71 specimens; 1244 h trawled) vessels trawled in 50-75 m and caught 10 and 7 species respectively. The Soela (41 specimens; 72.5 h trawled) and Clipper Bird (36 specimens; 103 h trawled) operated in depths of 19-198 m and each caught 12 species. Hydrophines (10 species plus one specimen from an undescribed taxon) represented 68.4% of the specimens. Aipysurines (6 species) were more common in samples from the North West Shelf (46.2% of taxa, 56.6% of specimens) than from the Timor and Arafura Seas (28.6% of taxa, 11.2% of specimens). Taiwanese boats on the North West Shelf (1980-90) and Thai boats in the Arafura Sea (1985-90) were estimated to have caught 49000 (� 5600) and 10000 (� 1250) sea snakes respectively. Trawl surveys (e.g. Soela and Clipper Bird) may be unsuitable for monitoring sea snakes, because approximately 25 surveys would be needed to detect a 20% exponential decline in absolute abundance.
Nutrient limitation of phytoplankton in the upper Swan River estuary, Western Australia
Authors: Thompson PA , Hosja W
Published: November 2005

During 1993-94 the phytoplankton community in the upper Swan River estuary had a peak chlorophyll a concentration of 57 mg m-3 during early summer (December 1993) and a second peak of 35 mg m-3 during late autumn (May 1994). Mid summer was characterized by low cell densities and low chlorophyll a concentrations. The potential of the phytoplankton community for nutrient limitation was assessed with dilution bioassays given nutrient mixes deficient in one of the following: nitrogen, phosphate, silicate, iron, trace metals, chelators, or vitamins. During the mid-summer period of low phytoplankton abundance, nitrogen was the nutrient with the greatest potential to limit algal biomass. During mid summer, ambient N:P ratios tended to be near unity and bioassays indicated that the available pool of N was up to 20 times more limiting to biomass development than was available P. Also during mid summer, bioassay treatments given no nitrogen and control treatments given no nutrients showed little growth, reaching chlorophyll a concentrations -1/30th of those given a full suite of nutrients. Chlorophyll a concentrations in the bioassay control treatments given no nutrients were correlated (r2 = 0.74) with measured surface nitrate concentrations; this suggested that nitrate inputs may be a major factor controlling phytoplankton biomass in this ecosystem. The correlation between surface nitrate concentration and rainfall (r2 = 0.69) further suggests that rainfall may be the most important mechanism supplying nitrate to the surface waters of this estuary.
Acidification of an estuarine tributary in eastern Australia due to drainage of acid sulfate soils
Authors: Sammut J , White I , Melville MD
Published: November 2005

Episodic acidification (pH <5) of estuarine tributaries caused by the oxidation of sulfidic floodplain sediments is widespread in eastern Australia. Drainage and flood mitigation works promote oxidation and the export of sulfuric acid and dissolved aluminium and iron into streams. This paper examines the acidification of a tidal reach on the Richmond River, New South Wales. Acid discharge is controlled by the floodplain water balance, drainage of shallow acid groundwater, and tidal floodgate operation. Floodgates store acid waters for more than six months. Acid discharges ranged from short pulses during light rains to ~950 t of sulfuric acid in a major flood that acidified the reach for over seven weeks. Extensive iron flocs accompanied acidification and coated the benthos. The chemistry of the reach reflected mixing of acid groundwater with upland waters and showed pH-dependent enhancement or depletion of species relative to chloride. Concentrations of monomeric aluminium were over 300 times larger than local (ANZECC) guidelines and 90 km of the river were acidified after floods. The estimated rate of sulfuric acid production from the floodplain is ~300 kg ha-1 year-1 and discharge may occur for over 1000 years. Management options are considered; however, the long-term consequences of acidification of tidal reaches are unknown.
Profile of a bloom of the cyanobacterium Cylindrospermopsis raciborskii (Woloszynska) Seenaya and Subba Raju in the Fitzroy River in tropical Central Queensland
Authors: Fabbro LD , Duivenvoorden LJ
Published: November 2005

The physical, chemical and biotic conditions before and during a bloom of predominantly coiled heterocystous C. raciborskii are described. Initial increases in the population of this species were associated with windy days and the first downward movement of the thermocline into an anoxic hypolimnion after an extended period of stable stratification and no flow. Exponential growth and bloom formation coincided with the amval and retention of first wet-season inflows into the river impoundment.
Cyanobacteria and rotifers dominated the planktonic assemblage and chytrids (cyanobacterial pathogens) were present when the cell density of cyanobacteria peaked. Grazing of the coiled forms that dominated during the bloom was not recorded, but the rotifer Brachionus angularis has been observed ingesting entire straight trichomes of C. raciborskii.
Distribution of calcareous nannoplankton near the Subtropical Convergence, south of Tasmania, Australia
Authors: Hiramatsu C , De Deckker P
Published: November 2005

The floral composition of living calcareous nannoplankton collected from surface waters near the Subtropical Convergence (STC), offshore south-eastern Tasmania, in January 1994 is presented. Emiliania huxleyi represented more than 90% of all coccolithophorids. Scanning electron microscopy showed a substantial increase in intraspecific variation of E. huxleyi, and in variation in coccolith size of Calcidiscus leptoporus, E. huxleyi type A and C. leptoporus (small), north of the STC.
It is postulated that the percentage abundance of these taxa may be used to determine the position andlor shift of the STC zone through time, and therefore may be of use for palaeoceanographic studies.
Intra- and inter-estuary differences in assemblages of fishes associated with shallow seagrass and bare sand
Authors: Gray CA , McElligott DJ , Chick RC
Published: November 2005

Differences in the assemblages of fishes associated with the seagrass Zostera capricorni and bare sand were assessed across eight estuaries spanning 300 km of the coast of northern New South Wales, Australia. Assemblages consistently differed between habitats in all estuaries, as species affinities within each habitat were relatively consistent. A greater diversity and abundance of fishes generally occurred over seagrass than over sand. Great variation in the abundances of individual species was evident but there were no consistent geographic (inter-estuary) effects. The abundances of most species varied as much between locations (0.5-2.0 km apart) within each estuary as among estuaries (15-300 km apart). Juveniles of economically important species occurred over seagrass (e.g. Rhabdosargus sarba, Acanthopagrus australis, Girella tricuspidata) and sand (e.g. Sillago ciliata). Before the true value of different nursery habitats to fisheries resources can be identified, the contribution of the juvenile fishes residing in the different nursery habitats to future (exploited) populations needs to be quantified.
Effects of feeding level and starvation on growth and water and protein content in juvenile redclaw crayfish, Cherax quadricarinatus (von Martens)
Authors: Gu H , Anderson AJ , Mather PB , Capra MF
Published: November 2005

Effects of feeding level and starvation on growth, water content and protein content were examined in juvenile Cherax quadricarinatus. Gain in body weight was positively related to feeding level. An increase in feeding level resulted in a decrease in water content and an increase in protein content. Although the majority of juveniles were able to tolerate starvation for at least 12 days, deprivation of feeding caused a loss of weight and a gradual decrease in protein content combined with a simultaneous increase in water content. Total protein content was reduced by 3.9% in juveniles starved for three days and by 8.3% in those starved for 12 days. Normal body protein content, however, was recovered within six days after subsequent feeding in juveniles that were deprived of food for 12 days.
Use of scale patterns to evaluate stocking success of silver perch, Bidyanus bidyanus (Mitchell), released at two different sizes
Authors: Willett DJ
Published: November 2005

A study was conducted to determine relative success of stocking silver perch (Bidyanus bidyanus) at two different sizes: 35 mm and 50 mm total length. By purposeful manipulation of growth rates of pre-stocked fish it was possible to induce unique markers in scale circulus patterns, thus differentially marking the two size-groups. The scale circulus data were acquired with automated video-digitizing equipment. Both size-classes were stocked into two south-eastern Queensland impoundments. Relative stocking success after two years was quantified by sampling surviving silver perch and using discriminant function analysis to assign individuals to their respective size-at-release groups. Relative survival of fish stocked at 35 mm and at 50 mm was not significantly different in either impoundment. Post-stocking growth rates of 35 mm fish were not compromised due to their smaller size at release. From a management perspective, this suggests that 35 mm is a more cost-effective release size of silver perch than 50 mm. This trial demonstrates the feasibility of using scale circulus patterns to differentially mark multiple groups of fingerlings for such controlled experiments.
Growth rates of five species of subtidal clam on a beach in the South Island, New Zealand
Authors: Cranfield HJ , Michael KP , Francis RICC
Published: November 2005

Growth rates of five species of New Zealand surf clams were estimated at Cloudy Bay, Marlborough, from analyses of sequential length-frequency samples with the computer program MULTIFAN and analyses of incremental growth of marked individuals with the computer program GROTAG. The von Bertalanffy parameters k and L∞ estimated by MULTIFAN were: Paphies donacina, 0.33 and 94.1; Spisula aequilatera, 1.01 and 60.3; Mactra murchisoni, 0.57 and 88; M. discors, 0.41 and 68; data for Dosinia anus could not be analysed reliably. These parameters estimated by GROTAG were: P. donacina, 0.35 and 84.8; S. aequilatera, 1.74 and 57.6; M. murchisoni, 0.58 and 80.6; M. discors, 0.54 and 61.5; D. anus, 0.36 and 61.6. The age-based growth estimated by MULTIFAN is not strictly comparable with the length-based growth estimated by GROTAG, but graphical comparisons show that both programs estimate similar growth rates for each species of surf clam. Interspecies differences in growth rates are hypothesized to be related to differences in species depth distribution within the surf zone. S. aequilatera, with the highest growth rate, is found just inshore of the primary wave break, where surf diatom abundance is postulated to be highest. An extension to the linear growth model of GROTAG that allows the predicted growth of larger animals to decline asymptotically to zero and never be negative is presented.