bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic relationships of eight species of Pacific tunas (Teleostei: Scombridae) inferred from allozyme analysis
Authors: Elliott NG , Ward RD
Published: November 2005

A phylogenetic analysis of eight species of Pacific tunas was made after examining allozyme variation at 23 muscle and liver enzymes encoded by 35 loci. The eight species of tuna were: Thunnus alalunga, albacore; T. obesus, bigeye; T. thynnus orientalis, northern bluefin; T. maccoyii, southern bluefin; T. albacares, yellowfin; Auxis thazard, frigate; Euthynnus affiizii kawakawa; Katsuwonus pelamis, skipjack. All species except the northern bluefin were also examined for variation at three eye-specific loci. The average heterozygosity per locus ranged from 0.038 (frigate) to 0.070 (bigeye). Genetic relationships were examined on the basis of the 35 loci screened in all species. Genetic identities among the five Thunnus species were high, averaging 0.864 and ranging from 0.788 to 0.923. Whereas the albacore appeared to be the most divergent of the Thunnus species (mean identity to other Thunnus species of 0.825, range 0.788-0.452), there was little differentiation between yellowfin, southern bluefin and northern bluefin tunas (mean identity 0.905, range 0.892-0.923), and phylogenetic analyses failed to resolve the branch order among the Thunnus species. The non-Thunnus tunas were quite divergent both from one another and from Thunnus species (mean identity 0.358, range 0.280-0.606). Diagnostic allozyme loci were identified, allowing the discrimination of all species.
Planktonic and microbial contributions to phosphorus release from fresh and air-dried sediments
Authors: Qiu S , McComb AJ
Published: November 2005

There was a fivefold increase in the concentration of P (dissolved reactive phosphorus) after intact sediment cores from North Lake, Western Australia, were air-dried and reflooded. Effects of plankton and microbial biomass on phosphorus release were investigated. Freshly killed plankton released P before drying, but less P was released when plankton biomass was air-dried. Bacteria were important contributors of P during drying and rewetting, and their contributions occurred through two processes: (I) when sufficient moisture and oxygen were available, bacteria rapidly removed soluble P from the water and incorporated it into the particulate phase, the amount of P taken up being positively correlated with bacterial respiration; and (2) upon drying, bacterially stored P was partly returned to the water, the release increasing with increasing bacterial uptake. The bacterial contribution of P upon drying was further investigated by sterilizing air-dried and wet sediments with a low dose of gamma irradiation (10 kGy). It was thus possible to discriminate among P contributed from the native (initial) microbial biomass (Pi) before drying, P released from the increased (developed) microbial biomass (Pii) during drying, and P stored in bacteria that had survived air-drying (Ps). It was estimated that air-drying killed about 76% of the microbial biomass. At relatively low external P concentrations (<1000 μg L-1), the increased P brought about by air-drying was mainly derived from killed microbial biomass.
Sampling techniques for reliable determination of trace metals in macrophytes and periphyton
Authors: McBride TP , Noller BN
Published: November 2005

Sampling techniques were developed to measure trace-metal concentrations reliably in the shoots of a submerged macrophyte, Najas tenuifolia, and its attached periphyton growing in the Magela Creek flood plain in monsoonal northern Australia. At each site, 30 samples were collected within an 8-m by 8-m quadrat in a pattern of five samples from each of six irregularly spaced points. Samples were collected underwater to include all periphyton present, and precautions were taken at all stages of processing to avoid contamination. Periphyton was dislodged for separate chemical analysis by sonication followed by vigorous shaking. A significant aspect was the large amount of periphyton, up to 35% of the total sample dry weight, associated with the Najas sp. Only a proportion, up to 43%, of this periphyton could be dislodged by the physical procedures used.
Trace metals were generally not present in the same concentrations in both the Najas sp. and the periphyton. The average trace-metal concentrations (μg g-1 dry weight) and standard errors measured in the Najas sp. (and periphyton) were cadmium 0.24 � 0.013 (0.093 � 0.012), copper 5.2� 0.25 (12 � 0.74), lead 0.93 � 0.084 (6.5 � 0.43), manganese 2500 � 110 (1500 � 110), uranium 0.24 � 0.023 (0.27 � 0.030), and zinc 38 � 1.0 (23 � 1.5). The significant differences in Najas sp. and periphyton trace-metal concentrations show the need to consider the effect of periphyton when sampling and reporting trace-metal concentrations in submerged macrophytes.
Occurrence of a New Zealand pea crab, Pinnotheres novaezelandiae, in five species of surf clam
Authors: Palmer P
Published: November 2005

In samples from 60 random stations in four depth strata along the Manawatu-Horowhenua coast north-west of Wellington, Pinnotheres novaezelandiae was found in Mactra discors, M. murchisoni and Spisula aequilateralis but not in Paphies donacina or Dosinia anus. This is the first record of P. novaezelandiae from M. murchisoni. The incidence of P. novaezelandiae in each of the three infested species of surf clam was compared. Significantly more pea crabs were found to infest M. discors than M. murchisoni or S. aequilateralis. In Mactra discors the occurrence of pea crabs decreased with increased depth. Carapace widths of pea crabs from M. discors were significantly larger than those from M. murchisoni and S. aequilateralis. No significant differences were found between the carapace widths of pea crabs from M. murchisoni and S. aequilateralis. Crab size was positively correlated to host shell length, with significantly larger crabs inhabiting significantly larger shellfish. Pinnotheres atrinacola was recorded for the first time from S. aequilateralis.
Factors influencing invertebrate drift in small forest streams, south-eastern Queensland
Authors: Kerby BM , Bunn SE , Hughes JM
Published: November 2005

Aspects of invertebrate drift were investigated in four small rainforest streams in south-eastern Queensland. Hourly sampling in two streams revealed low drift rates and no distinct diel patterns. This may have been a consequence of the low flows experienced during the study period. The drift was dominated by Simuliidae, Chironomidae and to a lesser extent Tasmanocoenis sp. (Caenidae) and Cheumatopsyche sp. 6 (Hydropsychidae). Additional studies were undertaken to examine why some individuals of particular taxa drift while others (of the same taxa) remain in or on the substratum. Analysis of the relative gut fullness of simuliid and chironomid larvae showed that a higher proportion of non-drifting individuals had full or nearly full guts compared with those in the drift. Hungrier individuals of these two taxa may enter the drift as a food searching mechanism. An analysis of limb loss of hexapod nymphs indicated that a disproportionate number of individuals in the drift had one or more limbs missing compared with those that remained in the benthos. These data support the hypothesis that invertebrates present in the drift are less fit than non-drifters.
Influence of natural fluctuations in seagrass cover on commercial prawn nursery grounds in a subtropical estuary
Authors: Halliday IA
Published: November 2005

Juvenile prawns were captured with a beam trawl from two intertidal seagrass sites (one sparsely and one densely vegetated) in Tin Can Bay, a subtropical estuary in south-eastern Queensland. The abundance and recruitment patterns of two commercial prawn species (Penaeus plebejus and Metapenaeus bennettae) were investigated. P. plebejus was the dominant species at both the sparse and dense seagrass sites. Die-back of the above-ground vegetation in the sparsely vegetated site coincided with a significant increase in the abundance of both P. plebejus and M. bennettae at this site. Natural loss of intertidal vegetation may cause an immediate reduction in the total fisheries value of an area because of fewer herbivorous commercial fish entering the area. In the longer term, this reduction in the fisheries value of the area may be compensated by an increase in value as a nursery ground for juvenile P. plebejus, thereby providing the potential for higher adult P. plebejus recruitment to local commercial fisheries and maintaining the overall value of the area.
Age and growth of the queen scallop, Equichlamys bifrons, in the D'Entrecasteaux Channel and Huon River Estuary, Tasmania
Authors: Wolf BM , White RWG
Published: November 2005

Growth of the queen scallop, Equichlamys bifrons, was examined at one site in the D'Entrecasteaux Channel and two sites in the Huon River estuary (Tasmania) by analysing growth rings on the shell and shell hinge ligament, tagging scallops, and using size-frequency techniques. Regular sampling of scallops revealed that shell growth of E. bifrons is seasonal, commencing in late spring and stopping in late autumn. During the remainder of the year, when the water temperature is below ~13�C, shell growth slows or stops and growth rings are formed on the shell and shell hinge ligament. The growth rings on the shell and hinge ligament of E. bifrons were verified as being annual by studying the growth of marked scallops. Long-term growth patterns were similar for E. bifrons from Middleton (D'Entrecasteaux Channel) and from Deep Bay (Huon River estuary). Tagging data collected over the 1992-93 growing season indicated short-term variation in growth between sites. Size-frequency distributions from Middleton and Deep Bay could not be interpreted because smaller scallops were scarce. Smaller size classes were present at Eggs and Bacon Bay (Huon River estuary) and the size-frequency distribution was resolved into age classes. Reasonable agreement was found between the von Bertalanffy growth parameters obtained from the size frequency, tagging, and growth ring data.
Reproduction and survival of Phyllorhiza punctata (Cnidaria: Rhizostomeae) in a seasonally fluctuating salinity regime in Western Australia
Authors: Rippingale RJ , Kelly SJ
Published: November 2005

Although medusae of the scyphozoan Phyllorhiza punctata are abundant in the Swan-Canning estuary during summer, they are absent when surface waters are dominated by low-salinity runoff water following winter rains. In the laboratory, scyphistomae of P. punctata are shown to survive in conditions of temperature and salinity that occur in the estuary during winter in waters deeper than 5 m. It is postulated that areas of deep water provide a winter refuge for scyphistomae and that asexual production of both ciliary buds and ephyrae enables rapid growth of the P. punctata population in the spring of each year.
Consequences of aggregated living in the ascidian Pyura stolonifera: Evidence for non-contact intraspecific competition
Authors: Dalby JE
Published: November 2005

Non-contact intraspecific competition was examined as a possible consequence of the aggregated distribution of the ascidian Pyura stolonifera near Melbourne, Australia. In a field experiment designed so that experimental individuals did not touch surrounding conspecific individuals, ascidians inside aggregations grew significantly more slowly than those outside aggregations: at the end of the 24-month experiment, the former animals had shorter body lengths, lighter bodies, lighter tunics, and lighter gonads. This is one of few conclusive demonstrations of the existence of this type of intraspecific competition in sessile marine invertebrates occupying hard substrata, and the only demonstration for ascidians.
Effect of exogenous hormones on reproductive behaviour in territorial males of a natural population of demoiselles, Chromis dispilus (Pisces : Pomacentridae)
Authors: Pankhurst NW , Carragher JF
Published: November 2005

Territorial male demoiselles (Chromis dispilus) engaged in egg brooding and defence were hand-netted from nest sites by divers and injected in situ with either des-Gly10 (D-Ala6) luteinizing-hormone-releasing hormone ethylamide (LHRHA), human chorionic gonadotrophin (hCG), 17α,20β- dihydroxy-4-pregnen-3-one (17,20βP), testosterone (T), or 11-ketotestosterone (11KT) in order to examine the effect of elevated plasma steroid concentrations on the transition from brooding to spawning display behaviour (when plasma concentrations of steroids are typically elevated). Blood samples were analysed for 17,20βP, T, and 11KT by radioimmunoassay. The effect of egg presence on behaviour was assessed by removing the eggs from the nests of some fish. Underwater injections with hCG, LHRHA or gonadal steroids all resulted in increases in plasma 17,20βP, T and 11KT concentrations but did not stimulate the transition from brooding to display behaviour. Egg removal resulted in vacation of the territory by most fish within 24 h. There was no evidence of transition from brooding to display behaviour during the period after egg removal over which fish remained at the nest. The results indicate that bioactive gonadotrophin-releasing hormone, gonadotrophin or gonadal steroids alone do not stimulate the transition from brooding to display and spawning behaviour in male demoiselles. Egg presence has a marked effect on the strength of association with the nest, but loss of eggs did not trigger the onset of display behaviour. It seems likely that a combination of events, including elevation of plasma concentrations of gonadal steroids and egg loss (hatching), stimulates the transition from brooding to display behaviour.
Preliminary study of the distribution and photophysiology of the temperate phototrophic sponge Cymbastela sp. from South Australia
Authors: Cheshire AC , Butler AJ , Westphalen G , Rowland B , Stevenson J , Wilkinson CR
Published: November 2005

The distribution and photophysiology of two forms of Cymbastela were investigated. One form, which fitted the description of C. notiana, was found in the gulf waters of South Australia. A second form was found on the protected sides of islands along the oceanic coast of Victor Harbor in South Australia. Both forms are rare but when present occur at depths of 5-15 m in association with foliaceous red and brown macroalgae.
A fully automated respirometer was used in situ to investigate the photokinetics of the oceanic form at West Island (SA) during winter (June 1993) and summer (January 1994). Owing to the rarity of this sponge only four samples, three in the winter and one in the summer, were investigated. This form of Cymbastela was capable of photosynthetically compensating on a net 24-h basis at 4.5 m depth in the winter, whereas it was a net producer at that depth during the summer. Photokinetic measurements were used to model the phototrophic production of this sponge. This model predicts that sponges would generally compensate at a depth of 11 m in winter. These results are tentative, however, because sample sizes are small owing to the rarity of this species.
Improved estimation, using neural networks, of the food consumption of fish populations
Authors: Lek S , Belaud A , Dimopoulos I , Lauga J , Moreau J
Published: November 2005

The aim of the present work is to improve the relevance of methods to predict the Q/B ratio (annual consumption of food Q relative to the biomass B of fish species), which is essential for any multispecies stock model based on trophic relationships. Two methods were considered: multiple linear regression (MLR), improved by the log transformation of some variables, and artificial neural networks (NNs), which have the advantage of accepting nonlinearity in the relations between Q/B and different independent variables. Although MLR is acceptable for predicting small values of Q/B (mainly carnivorous fish), it does not display good performances for high values (herbivorous and detritivorous fish). In contrast, by using the gradient back-propagation algorithm, the NNs are suitable for a valid estimation of the whole range of known values of Q/B. Both types of model were tested with test sets of data (drawn at random from the full set of data) that had not been used for model construction. The proposed methods are thus predictive. As they require only a few easily accessible parameters, they can avoid tedious studies of fish feeding over a daily and an annual cycle. The NN program used, operating on a personal computer, is available on request.
Patterns in subtidal marine assemblages associated with a deep-water sewage outfall
Authors: Roberts DE
Published: November 2005

The macrobenthic assemblages living on hard substrata in the vicinity of the Sydney deep-water ocean outfall at North Head were sampled from March 1991 to April 1994. The main objective of the study was to determine whether spatial and temporal patterns in macrobenthic diversity and abundance were affected by the outfall. The assemblages were sampled according to an experimental design that had three sites nested within each of three locations. These locations were North Head (outfall location), Long Reef and Bungan Head (control locations). Ten replicate quadrats at each site were photographed with a jump camera. These photographs were then sampled to provide estimates of the number and abundance of the major component phyla and also abundances of individual species. An asymmetrical analysis of variance detected a significant time × outfall versus control interaction for the total number of species, bryozoans and cnidarians and for the abundances of two bryozoan species and a silt matrix. Smaller-scale interactions among sites through time occurred for many taxa, representing both inherent 'noise' and some evidence for outfall effects at these smaller spatial scales. This study demonstrates that there is correlative evidence of an effect of the outfall, but in general the assemblages showed various spatial and temporal fluctuations that should not be attributed to sewage.
Effects of training on observer performance in assessing benthic cover by means of the manta tow technique
Authors: Miller IR , De'ath G
Published: November 2005

The manta tow technique is used to obtain broadscale information on the distribution of Acanthaster planci and corals on the Great Barrier Reef. A field experiment was used to investigate how experience and training affects visual estimates of benthic cover made by observers using the manta tow technique. For live coral and sandlrubble cover, experienced observers obtained significantly higher levels of precision in their estimates than inexperienced observers; training increased the precision of these estimates for both experienced and inexperienced observers. Dead coral cover was sparse (<5%), making it difficult to assess the performance of the manta tow technique for this form of benthic cover. For both live and dead coral, and for sandlrubble, the levels of agreement between observers exceeded that expected by chance by between 5 to 1 and 10 to 1.
Microbial consortia in wetland sediments: a biomarker analysis of the effect of hydrological regime, vegetation and season on benthic microbes
Authors: Boon PI , Virtue P , Nichols PD
Published: November 2005

Microbial consortia in the sediments from a permanent wetland near Albury-Wodonga in north-eastern Victoria, Australia (Ryans 1 Billabong), and an ephemeral wetland near Shepparton in central Victoria (Raftery's Swamp) were quantified by analyses of phospholipid fatty acid (PLFA), polar lipid ether lipid (PLEL), sterol and alcohol profiles. Prokaryotic organisms dominated the benthic assemblages in both wetlands. Total prokaryotic abundance (i.e. eubacteria plus archaea) was estimated to be (7-17) × 109 cells g-1 sediment (dry weight). Methanogenic archaea were estimated to number (1-5.4) × 109 cells g-1 and to account for 11-36% of the total benthic prokaryotes; these values are apparently among the highest recorded for temperate lake or river environments. PLFAs indicative of specific metabolic groups (e.g. sulfate-reducing bacteria (SRB), methanotrophic bacteria, etc.) were also detected. The PLFA profiles indicated that Type I methanotrophs (abundant in C16 PLFAs) were more abundant than the Type II group, which contain C18 PLFAs. Acetate-utilizing SRB were more abundant than were lactate-utilizing SRB, but neither group was dominant. Ergosterol was not detected, which suggested that fungi were not a significant component of the benthic microbial consortia in spite of both wetlands having abundant inputs from aquatic and fringing vascular plants. Other biomarkers, such as sterols, long-chain alcohols, triterpenoids and phytol, demonstrated inputs from these higher plants. PLFA, PLEL and sterol profiles indicated that benthic microbial consortia were affected by hydrological regime, the presence of aquatic vegetation, and season. Information from this preliminary study may assist in the making of informed management decisions on environmental water allocations for natural ecosystems.
Stock-recruitment relationships and the precautionary approach to management of tropical shrimp fisheries
Authors: Garcia SM
Published: November 2005

This paper examines the possibilities and implications of using precautionary management approaches to deal with the uncertainty regarding the stock-recruitment relationships in tropical shrimp fisheries. After a brief review of the stock-recruitment problem and related reference points in these fisheries, and in the precautionary approach in general, it proposes an empirical approach to the stock-recruitment relationship as a basis for the determination of safe and risky fishing mortality levels. It illustrates a management strategy based on the seasonal escapement of spawning biomass. Finally, it offers a discussion on the robustness of the empirical approach and on its validation using additional information.
White shrimp (Penaeus setiferus) recruitment overfishing
Authors: Gracia A
Published: November 2005

White shrimp, Penaeus setiferus, is one of the major species exploited in the Gulf of Mexico. Annual catches reached a peak of 1200-2000 t during 1970-80. In the following years, there was a marked decline that took the fishery to less than one-fifth of its highest production levels. Decline was associated first with decreasing fishing power of the fleet and later with the establishment of a new artisanal drift-net fishery. The artisanal fishery has the following characteristics: it acts selectively on spawners older than eight months, its fishing effort increases during spawning periods when white shrimp school and are more vulnerable to drift-nets, and it has displayed an explosive growth rate due to the high profitability. Previous evidence of a spawning stock-recruitment relationship for white shrimp suggests that a recruitment failure had taken place. The relationship between spawning and recruitment, based on the main cohorts of the two annual generations, exhibited a negative tendency that drove the stock down to near-critical spawner biomasses. Environmental influences on recruitment, although important for annual variations, are unlikely to be responsible for this decline. Decline in yield may be attributable to recruitment overfishing, as spawning stock was reduced to almost 8% of virgin biomass. White shrimp have a high resilience to overfishing, as the stock displayed a quick recovery after the artisanal fishing effort decreased. Managing white shrimp with a precautionary approach requires the maintenance of spawning stock at more than 17-20% of virgin biomass.
Identifying tropical penaeid recruitment patterns
Authors: Watson RA , Turnbull CT , Derbyshire KJ
Published: November 2005

Knowledge of recruitment patterns is a requisite for modern fisheries management. These patterns can range in complexity from a single pulse of identically sized and aged prawns, which is often assumed in fisheries models, to continuous recruitment by prawns of several ages. Existing techniques used to identify recruitment patterns range from the ad hoc use of size limits to more complex methods that examine changes in length-frequency modes through time.
A model that allowed variable growth of individuals was used to simulate monthly length-frequency fisheries data from a range of recruitment patterns of varying complexity. The effectiveness of a range of methods to identify these underlying recruitment patterns was examined. Length-frequency survey data from tropical penaeid fisheries for Penaeus esculentus, the brown tiger prawn, in two locations off north-eastem Australia (Torres Strait and Turtle Island Group) were also subjected to these methods.
Methods that employed simple truncation by length successfully identified simple recruitment patterns but were not effective for multi-age recruitment patterns. Only the length-cohort and age-cohort methods could identify the presence of older recruits in multi-age patterns. All methods were sensitive to estimates of growth parameters, particularly the cohort-based methods. Results suggest that P. esculentus from the two fisheries examined had different recruitment patterns requiring different management approaches.
Diet Niche Relationships among Early Life Stages of Fish in German Estuaries.
Authors: Thiel R , Mehner T , Kopcke B , Kafemann R
Published: November 2005

Diet composition, selectivity, food niche width and food niche overlap of early life stages of fishes were studied in the Barther Bodden system and in the Weser and Elbe estuaries during spring and summer from 1987 to 1991 and from 1993 to 1994.
Larvae of perch (Perca fluviatilis) and roach (Rutilus rutilus) dominated in the Barther Bodden. Herring (Clupea harengus) and perch were the dominant species in the Barther Strom. Smelt (Osmerus eperlanus) was the most common species in the Elbe estuary. Sprat (Sprattus sprattus) was of most importance in the Weser estuary.
The dominant prey of fish larvae were copepodids, nauplii and eggs of Eurytemora afinis. The highest food niche width was observed for nine-spined stickleback (Pungitius pungitius), ruffe (Gymnocephalus cernuus), three-spined stickleback (Gasterosteus aculeatus) and perch in the Barther Bodden. Negative selectivity indices indicated that populations of rotifers were scarcely influenced by predation by fish larvae. In contrast, E. affinis was preferred by early life stages of fish. Positive relationships were estimated between maximum prey lengths and predator lengths of different fish species.
Key species with regard to niche overlap were nine-spined stickleback, roach, three-spined stickleback and perch in the Barther Bodden, perch and herring in the Barther Strom, herring and three-spined stickleback in the Elbe estuary, and sprat and common goby (Pomatoschisrus microps) in the Weser estuary. High geographical overlap between fish species occurred in the Elbe estuary and Barther Bodden, whereas high diet overlap was estimated for both the Weser estuary and Barther Strom.
Modelling Penaeid Prawn Larval Advection in Albatross Bay, Australia: Defining the Effective Spawning Population
Authors: Rothlisberg PC , Craig PD , Andrewartha JR
Published: November 2005

A 3-dimensional numerical circulation model was linked to four larval-postlarval behaviour patterns to establish the origins of postlarvae recruiting into the estuaries adjacent to Albatross Bay, Gulf of Carpentaria, Australia. The area from which these postlarvae originate is called the 'advective envelope' and it delimits the spatial extent of the effective spawning population. The different behaviour scenarios vary the amount of time the postlarvae are active during the flood tide and the depth at which they change between their diel and tidal activity patterns (transition depth). The envelope with a behaviour scenario that incorporated a 20 m transition depth and a 3 h tidal activity pattern was 1000 km2. Incorporation of seasonal winds changed the shape but not the extent of the advective envelopes.
Distribution of Larval and Juvenile Fish in the Western Irish Sea: Relationship to Phytoplankton, Zooplankton Biomass and Reccurrent Physical Features
Authors: Dickey-Collas M , Gowen RJ , Fox CJ
Published: November 2005

In the western Irish Sea, differences in tidal currents and water depth create seasonal hydrographic regions. The summer stratified region has an associated cyclonic gyre of near-surface water. Each region has a distinct seasonal cycle of phytoplankton production, and the coastal region is one of the most important fish spawning areas in the Irish Sea. The abundances of larval fish and newly metamorphosed pelagic juveniles were negatively and positively correlated with depth, respectively, suggesting that fish that spawn in the coastal region do not spend all of their early life stages inshore. The distribution of larvae and 0-group pelagic fish reflects the close coupling between recurrent hydrographic features and biological production. The coastal region supports early and sustained primary production and generally a higher biomass of zooplankton in early spring than the offshore mixed and stratified regions. Later in the year, pelagic 0-group fish are associated with a greater biomass of zooplankton in the summer stratified region. The movement of pelagic 0-group fish into the summer stratified region may result from the entrainment of a southerly flow of coastal water into the western Irish Sea gyre. The seasonal gyre may physically retain these pelagic fish within the western Irish Sea during the summer.
Do Thermoclines Explain the Vertical Distributions of Larval Fishes in the Dynamic Coastal Waters of South-eastern Australia?
Authors: Gray CA
Published: November 2005

This study examined whether the position and strength of the thermocline influenced the vertical distributions of larval fishes in the coastal waters off Sydney. Depth-stratified sampling of larval assemblages was done in stratified and non-stratified conditions. Larval assemblages were depth- stratified, and individual taxa displayed specific depth distributions in all types of water columns. In stratified and non-stratified water columns some species were characteristic of shallow, mid and deep depth strata. The presence of a thermocline did not appear to influence broad-scale patterns of vertical distribution of larval fishes, and it was not considered a good predictor of larval vertical distribution. Larval behaviour appeared to be the major influence determining vertical distributions of larval fishes. It is argued that thermoclines may not be important to larval fishes in waters characterized by dynamic oceanography, such as those off Sydney, where the position and integrity of the thermocline can vary greatly over small temporal and spatial scales. Greater emphasis needs to be placed on teasing out the importance of various interacting biotic and abiotic features of the water column in structuring vertical distributions of larval fishes.
Testing protein-walled microcapsules for the rearing of first-feeding gilthead sea bream (Sparus aurata L.) Larvae
Authors: Yufera M , Sarasquete MC , Fernandez-Diaz C
Published: November 2005

Two basic types of protein-walled microcapsules were developed with the aid of using different preparation techniques. One type (Type A) was spherical and hard-walled, whereas the other (Type G) was irregularly shaped and soft-walled. The present work examined the larval growth and development of Sparus aurata reared either with these microcapsules as the sole food source or with a mixed diet of microcapsules and rotifers from the start of feeding. Larvae fed on Type A microcapsules evacuated them practically intact. These larvae showed strong degeneration of the gut epithelium, liver and pancreas and died within two to three days after the onset of feeding. In contrast, larvae fed from first feeding with Type G microcapsules alone ingested and broke down the particles from the onset of feeding. No larval growth was observed, but some larvae were still alive at the end of the experiment (Day 13). Larvae reared with a mixed diet, including Type G microcapsules and a small amount of rotifers (0.5 rotifer mL-1), showed in general normal development of gut epithelium. These larvae had good growth but survival was reduced to one-half of that obtained under routine rearing of larvae fed on rotifers alone.
Type G microcapsules appear to represent an adequate departure point for the development of an inert diet able to support larval growth in marine fish.
Development of techniques for the large-scale rearing of the larvae of the Australian freshwater fish golden perch, Macquaria ambigua (Richardson, 1845)
Authors: Rowland SJ
Published: November 2005

Experiments were conducted over four consecutive breeding seasons. Golden perch, Macquaria ambigua, larvae (total length, 5.0 mm) held at 23� to 25�C, commenced feeding on crustacean zooplankton (<350 pm in length) five days after hatching, at age D6 (D1 = day of hatch). Zooplankton density had a significant effect (P < 0.01) on the survival of larvae in 70-L aquaria. A delay of only two days to age D8 in initial feeding significantly reduced (P < 0.01) survival, and larvae not offered zooplankton until D10 did not commence feeding. There was a positive linear relationship (r2 = 0.98) between survival in earthen ponds (0-57.6%) and the volume of small zooplankton sampled from the ponds at stocking, but survival was not affected by larval stocking density (32-365 m-2) or length of the culture period (28-53 days). A mean survival of 44.6% in ponds that were left dry over winter and then stocked 10-14 days after filling, was significantly higher (P < 0.01) than survival in ponds stocked only 2-5 days after filling or in ponds inundated during winter. Survival, growth and production were not significantly different among ponds fertilized with inorganic fertilizer (NPK) alone or in combination with lucerne hay or poultry manure. Larvae grew at rates of 0.5-1.1 mm day-1, production rates were up to 153 kg ha-1 and a maximum number of 271 000 juveniles were reared in a 0.3 ha pond. Approximately 3 × 106 golden perch are produced annually at hatcheries in eastern Australia using techniques developed during this study.
Histological Investigation of Swim-bladder Morphology and Inflation in Cultured Larval Striped Trumpeter (Latris lineata) (Teleostei, Latridae)
Authors: Goodsell A , Wikeley D , Searle L
Published: November 2005

Histological techniques revealed that primary swim-bladder inflation in Latris lineata, a Tasmanian marine finfish, occurred before first feeding (Days 6 to 8 after hatch, depending on culture conditions). The histological appearance of the swim-bladder altered markedly after inflation; the lumen lining changed from columnar epithelium to predominantly squamous epithelium with an anterior crescent of cuboidal epithelial cells forming the gas gland. The pneumatic duct traversed ventrally from the posterior end of the swim-bladder and entered the intestine at the junction of the oesophagus and the intestine. The columnar epithelium persisted in non-inflated swim-bladders, and proliferation of the underlying vascular system caused the epithelium to fold and fill the entire lumen.
Spatial Variability of Recent Otolith Growth and RNA Indices in Pelagic Juvenile Diaphus kapalae (Myctophidae): an Effect of Flow Disturbance near an Island?
Authors: Suthers IM
Published: November 2005

In February 1993, the pelagic juvenile myctophid Diaphus kapalae was sampled with a neuston net in the southern Coral Sea in a region of flow disturbance north of Cato Reef, and to the east in the free stream (northerly flow at 30 cm s-1). There was no significant difference in the size (11-16 mm SL) or age (45-74 days after hatching) between the two regions. Recent growth indices derived from the width of the peripheral daily growth increments (~10 μm each) revealed enhanced otolith growth 38 km downstream and up to 4 days before capture. No significant difference was found for times longer than a week before capture, consistent with fluctuation of the wake indicated from current-meter data. Daily increment formation was confirmed by marginal increment analysis. Recent otolith growth was correlated with the RNA content adjusted by dry weight, which also revealed significantly higher condition in the wake region. Recent growth was correlated with microzooplankton biomass, recorded with an optical plankton counter.
Application of RNA : DNA Ratios to Evaluate the Condition and Growth of Larval and Juvenile Red Drum (Sciaenops ocellatus).
Authors: Rooker JR , Holt GJ
Published: November 2005

RNA:DNA ratios in individual red drum (Sciaenops ocellatus) were measured in laboratory-reared larvae and juveniles (6-20 mm standard length; age 16-40 days) to assess the effects of growth, starvation, and diel periodicity on biochemical condition. RNA: DNA ratios were correlated positively with both absolute (mm day-1) and instantaneous (% day-1) growth rates. The effect of starvation was evaluated daily over 5 day periods at three ontogenetic stages (20, 30, and 40 days). Significant differences in RNA:DNA ratios of fed and starved larvae were observed and changes in biochemical condition were detected statistically within 1 to 2 days of food deprivation. RNA:DNA ratios decreased continuously over the entire 5 day starvation period, with relative reductions in RNA : DNA ratios decreasing with increasing age. Diel variations in RNA : DNA ratios were investigated in controlled (constant) and natural (cyclical) temperature environments over a 48 h period. RNA: DNA ratios were highest during daytime periods (0800, 1200, 1600, 2000 hours) and markedly reduced at night (0000, 0400 hours). Since RNA: DNA ratios from controlled and natural temperature treatments did not differ significantly, cyclical variations in temperature did not appear responsible for diel variations in biochemical condition. Findings from this study support the use of nucleic acids as reliable indices of growth and condition and suggest that RNA: DNA ratios are potentially suitable measures to assess the condition of wild-caught S. ocellatus.
Effect of Experimental Manipulation of Feeding Conditions on the Population Stucture of Larval Cod (Gadus morhua) and Herring (Clupea harengus).
Authors: Geffen AJ
Published: November 2005

Cod and herring larvae were fed either rotifers or mixtures of rotifers, Artemia, and wild plankton to test the effects of feeding conditions on the development of population size structure. The population size structure at each sample date was characterized by the skewness, the standard deviation of mean length, the coefficient of variation of mean length and the Gini coefficient. The development of size structure through time was characterized by the spreading rate, which is the rate of change in the standard deviation of mean length over time. Larvae fed on a single, small-sized prey item (rotifers) grew slowly, and size variation increased slowly. Larvae fed on mixed prey species showed better growth; the population structure changed more rapidly, and often led to a skewed size distribution dominated by larger individuals. The presence of larger prey items resulted in disproportionate growth rates in the mixed-diet groups. The presence of these faster-growing individuals was the most important factor in determining the shape of the final size distributions and the development of the population size structure.
On Bluefish (Pomatomus saltatrix L.) Spawning in the Black Sea
Authors: Gordina AD
Published: November 2005

Until quite recently there were no reliable data on bluefish spawning in the Black Sea. The present study showed that bluefish spawned throughout the Black Sea from June to mid September at temperatures from 20� to 26�C and salinities from 17 to 20. Egg abundance did not exceed 12 eggs per m2, and larvae were less numerous.
Aspects of Life History and Management of Tailor (Pomatomus saltatrix) in Queensland
Authors: Zeller BM , Pollock BR , Williams LE
Published: November 2005

Tailor (Pomatomus saltatrix) is an important commercial and recreational species. Published and unpublished information on the reproductive biology and seasonal migrations of P. saltatrix in southern Queensland are summarized for 1978-93. Gonad index (GI) data from commercial ocean beach catches gave mean monthly values for fish ≥ 250 LCF (length to caudal fork; n = 389), decreasing from January to April before increasing to a peak in November. R saltatrix taken on Fraser Island in September and on South Stradbroke Island in November had high GI values. Adult fish in spawning condition were captured, tagged and released (n = 7090) on Fraser Island beaches in 1978-80 and 1987-89. Most tagged fish dispersed southward, being recaptured within 400 km of the tagging point. Gonad maturity at tag release and recapture locations and egg concentrations in plankton tows identified a major spawning area for P. saltatrix as the inshore waters between Indian Head and Waddy Point, Fraser Island. Although it is generally accepted that the eggs and/or larvae move southward with the East Australian Current (EAC), distribution and movement of larval P. saltatrix in Queensland waters are not known. Juveniles inhabit and move extensively throughout estuaries to the south of Fraser Island until recruitment as adults on ocean beaches. Recent stock management strategies in Queensland include a minimum legal size of 300 mm (total length), an annual one-month (September) closure to all forms of fishing in the spawning area identified on Fraser Island and input controls on fishing effort of commercial ocean-beach net fishers. Bag limits for recreational anglers may be introduced.
Distribution of Tailor (Pomatomus saltatrix) Larvae along the Coast of New South Wales, Australia
Authors: Miskiewicz AG , Bruce BD , Dixon P
Published: November 2005

The distribution of tailor (Pomatomus saltatrix) larvae is described on the basis of the results of four plankton surveys undertaken in northern and central New South Wales (NSW) coastal waters. These comprised a single survey during May 1989 along the northern NSW coast and multiple surveys in January, March and May 1983 between Sydney and Brisbane. Pomatomus saltatrix larvae occurred throughout the survey period, with the highest abundances on the northern NSW coast. Most larvae were caught in mid and outer continental shelf waters at water temperatures of ≥22�C. The only known spawning locality for P. saltatrix is in the vicinity of Fraser Island in southern Queensland from August to October. The occurrence of larvae along the NSW coast from January to May indicates that the spawning season of P. saltatrix is more extensive than previously reported and that spawning occurs along the east coast of Australia in localities other than Fraser Island. Further surveys of larvae in southern Queensland and northern NSW waters, especially from August to December, are required to determine if P. saltatrix has one extended or two discrete spawning seasons along the eastern coast of Australia.
Tailor (Pomatomus saltatrix) off Western Australia: where does it Spawn and how are the Larvae Distributed?
Authors: Lenanton RC , Ayvazian SG , Pearce AF , Steckis RA , Young GC
Published: November 2005

Tailor is a key finfish resource in Western Australia and is heavily exploited, but there has been no information either on the location and timing of spawning of the species in these waters or on the subsequent distribution and movements of the larvae. The present study has reviewed the literature to elucidate where tailor typically spawn and in which salinities and water temperatures they are most likely to be found. These data have then been collated with new data on the biology of juvenile and adult tailor in Western Australia, and on the salinities, temperatures and water movements off the coast. This has enabled a hypothesis to be developed delineating where spawning is likely to occur in this region and where the larvae are distributed. It is proposed that spawning occurs in inner-shelf waters between spring and autumn. Eggs and larvae are most likely to be transported to coastal nursery areas by wind-driven northward coastal currents that predominate during the main spawning period.
Genetic Relationships among Geographically Isolated Populations of Bluefish (Pomatomus saltatrix)
Authors: Goodbred CO , Graves JE
Published: November 2005

Restriction fragment length polymorphism (RFLP) analysis of mitochondrial DNA (mtDNA) was employed to elucidate genetic relationships among six geographically isolated populations of bluefish (Pomatomus saltatrix). MtDNA haplotypes based on nine informative restriction endonucleases were generated from samples of approximately 20 bluefish each from Portugal, Brazil, South Africa, western Australia and eastern Australia, and analysed with previous data for 472 bluefish from the east coast of the USA and 19 from eastern Australia. Considerable genetic variation was evident within most populations, with haplotype (nucleon) diversities ranging from 0.104 to 0.924 (mean 0.686, pooled 0.917) and nucleon sequence diversities ranging from 0.05% to 0.71% (mean 0.42%, pooled 1.09%). No mtDNA haplotypes were shared among samples, although some haplotypes from isolated populations were quite similar, differing by one or two restriction site changes. Net nucleotide sequence divergences between samples ranged from 0.26% (USA v. Portugal) to 1.75% (Brazil v. western Australia). Clustering of nucleotide sequence divergences indicated that bluefish from the United States, Portugal and South Africa were closely related, as were those from eastern and western Australia. The Brazilian sample was distantly related to all other groups. Neighbour-joining and parsimony analyses of restriction site data supported the groupings based on nucleotide sequence divergences and suggested that a low degree of historical mixing may occur among closely related populations. Migration between isolated populations, though very limited, could result from long-distance dispersal of early life-history stages or movements of vagile adults during times of suitable temperate distributions.
Life History and Fishery of the Enchova, Pomatomus saltatrix, in Southern Brazil
Authors: Haimovici M , Krug LC
Published: November 2005

Landings of the enchova, Pomatomus saltatrix, along the south-western Atlantic coast from Rio de Janeiro (23�S) to Argentina (38�S) averaged about 5000 t (1970-92) and attained a peak of about 15000 t in 1971. Most catches were with purse-seines and gill-nets along the coast of southern Brazil and were of immature and young adult enchovas moving northward in winter toward lower latitudes. Ring formation on scales occurs in winter in association with low water temperature and decreased feeding activity; the maximum observed age was 8 years and the largest specimens measured up to 800 mm total length (TL). Both young of the year and older enchovas fed on fishes and squid. Off southern Brazil, enchovas are multiple spawners from mid spring to late summer and first maturity is attained in the third year of life at 350 to 400 mm TL. P. saltatrix specimens from southern Brazil and Argentina seem to belong to a single stock, and observed migration patterns show similarities to those in other regions: movement toward lower latitudes in winter when surface temperatures decrease and toward higher latitudes in late spring and summer along both shelf and slope.