Ingestion and ejection of hooks: effects on long-term health and mortality of angler-caught yellowfin bream Acanthopagrus australis

Ninety juvenile yellowfin bream Acanthopagrus australis were angled from holding tanks, allowed to ingest nickel-plated, carbon-steel J-hooks and released (with their lines cut) into individual experimental tanks during 2 experiments in order to assess their (1) long-term (up to 105 d) health, mortality and rate of hook ejection and (2) short- and medium-term (< 42 d) temporal changes in health during hook ingestion. Equal numbers of control fish were scooped from holding tanks and similarly monitored in experimental tanks. Of 20 hook-ingested fish released during Expt 1, 3 died within 8 d, providing a non-significant mortality of 15%. Between Day 6 and Day 56 post-release, 13 of the surviving individuals ejected their hooks, which were typically oxidized to about 94% of their original weight and often broken into 2 pieces. At Day 105, there were no significant differences between the 20 control and 17 hook-ingested/-ejected fish in terms of their ability to digest and assimilate food (measured as changes in apparent digestibility coefficients), stress (measured as concentrations of plasma cortisol and glucose) or of morphological parameters that included weight (Wt) and maximum height (MH), maximum width (MW) and maximum girth (MG). During Expt 2, 3 individuals that still contained ingested hooks and 3 controls were sampled on each of 9 occasions between Day 3 and Day 42 post-release. All fish were sampled for blood cortisol and glucose and were then euthanized before being weighed and measured for total length (TL), MH, MW and MG. Hook-ingested individuals were also X-rayed to determine the position and orientation of hooks. There were no significant differences in plasma glucose between hook-ingested and control fish. Irrespective of the treatment of fish, concentrations of cortisol were elevated on some sampling occasions, indicating variable, acute stress. The MH and MG of fish were not significantly different between groups. Significant differences were detected for MG and Wt, with hook-ingested fish having weights similar to those of the control fish but a relatively greater MW (owing to stomach distension from ingested hooks) until 2 wk post-release, after which both morphological parameters generally declined. There was no significant temporal progression of hooks in the stomach of treatment fish; however, some hooks reorientated to positions that may have precluded passage along the digestive tract. We conclude that, for the J-hooks examined, cutting the line is an appropriate strategy that results in the greater majority of released hook-ingested yellowfin bream surviving with minimal negative long-term effects.     

Effects of angler-induced exercise and air exposure on the mortality of mouth-hooked yellowfin bream (Acanthopagrus australis)

Two aquaria experiments were done to quantify the short-term (up to 10 days) mortality of mouth-hooked yellowfin bream ( Acanthopagrus australis ) after short and long playing times (5 vs 30 s) followed by different extremes in air exposure (2.5 vs 5 min). During exp. 1, 44 fish were angled from randomly-selected 5000-L holding tanks, played for 5 s, subjected to either 2.5 or 5 min air exposure and then released into replicate sea cages located in a 1050 KL pool. Appropriate numbers of controls were transferred without air exposure from an unfished 5000-L tank into separate cages in the pool. The same methodology was applied during exp. 2, except that 31 yellowfin bream were angled and played for 30 s (rather than 5 s) before being subjected to the different durations of air exposures and released. Fish were monitored for 10 and 5 days in exps. 1 and 2, respectively. Concentrations of plasma cortisol and glucose were collected from samples of fish on the first and last days of the experiments. The only mortalities were two individuals (one from each treatment) during exp. 2, attributed to clotted blood (from hook wounds) across the gill lamellae. Surviving individuals at the end of the experiments had variable elevations in plasma cortisol but not glucose, indicating acute stress responses that were probably evoked during sampling. The conclusion is that yellowfin bream are resilient to being mouth-hooked, exercised and exposed to air before being released. However, to minimise impacts, individuals should be released as soon as possible, especially when blood is present at the hook wound.     

Spermatozoal ultrastructure of four Sparidae fishes: Acanthopagrus berda, Acanthopagrus australis, Lagodon rhomboids and Archosargus probatocephus

The mature spermatozoa of two Taiwan protandrous hermaphrodite Sparidae Acanthopagrus berda and Acanthopagrus australis are investigated and compared with those of other two Sparidae (Lagodon rhomboids and Archosargus probatocephus) from the Western hemisphere. Ultrastructurally the spermatozoon of these four species has a spherical, homogeneously electron-dense nucleus with an axial nuclear fossa. The midpiece contains one to four spherical mitochondria and encircles the basal body of the flagellum. The mature spermatozoa of the four species are of the primitive or ect-aquasperm form and conform to the teleostean type I spermatozoon with the flagellar axis inserts perpendicular and medial to the nuclear fossa. Variation in the depths of the nuclear fossa and mitochondria number is substantial in these four Sparidae species. This study provide useful systematic characters to the existing knowledge of comparative spermatology of Sparidae.     

Changes in monogenean and copepod infestation on captive Acanthopagrus australis (Sparidae)

Infection levels by 17 species of ectoparasite on 491 yellowfin bream collected throughout 1990 from Moreton Bay, S.E. Queensland were compared to infections on 82 bream collected during the same period from a captive population in a large pond at Sea World, Gold Coast, Queensland. There was a significant increase in prevalence and/or intensity of monogeneans Lamellodiscus acanthopagri and Polylabroides multispinosus , but a decrease in the monogenean Anoplodiscus australis and the copepods Ergasilus australiensis, Lernanthropus atrox, Bomolochus stocki and Alella macrotrachelus on captive fish. Twenty-eight bream collected from the pond during autumn were placed in an experimental 1 m³ cage within the pond for 4–6 weeks. Compared to the baseline data for the pond, the caged fish showed increased prevalences of the monogeneans Lamellodiscus acanthopagri, L. squamosus, L. major and Haliotrema spariensis , and increased intensities of L. squamosus, Allomurraytrema robustum and P. multispinosus. The copepod Caligus epidemicus dropped off in preservative, but its abundance (average number per fish) was significantly higher on caged fish than on pond or wild fish. Increased infection levels by L. acanthopagri and A. robustum were due in part to autoinfection. The large skin area promoted large populations of C. epidemicus.     

Observations on the attachment by the monogenean, Anoplodiscus australis, to the caudal fin of Acanthopagrus australis

The unarmed haptor of Anoplodiscus australis erodes the epidermis and attaches to the basal lamina above the stratum compactum in the caudal fin of Acanthopagrus australis by an eosinophilic, weakly PAS-positive and strongly toluidine blue-positive secretion. Ultrastructural evidence shows that the adhesive secretion, in the form of rod-shaped bodies, is produced by subtegumentary cells that connect by ducts to the thin, ventral syncytial tegument of the haptor; these bodies pass into the tegument, then coalesce in the host-parasite interface. This means of attachment has developed by an enhancement and regional specialization of the subtegumentary secretory cells associated with a syncytial tegument in monogeneans and some other platyhelminths. The available evidence indicates that the adult parasite is permanently attached.     

New pathological condition in cultured mulloway Argyrosomus japonicus: histopathological, ultrastructural and molecular studies

Mulloway Argyrosomus japonicus is a native fish species in Western Australia, for which aquaculture production has recently been developed. A single cohort was stocked in a cage offshore at Geraldton, Western Australia, at a water depth of 6 m. Fish appeared healthy before stocking. Routine histological analysis was carried out from 10 mo post stocking and until completion of harvest (about 2.5 yr post stocking). No gross pathology was evident. Microscopically, however, granulomatous lesions were present in the kidneys of almost 100% of the fish examined. Enclosed in the granuloma was an aggregate of organisms, 4.2 to 5.4 μm in diameter. Kidney granulomas appeared as multi-focal aggregates. Granulomas at different stages of formation and finally fibrosing granulomas were observed. Granulomas also appeared infrequently in other organs: a few granulomas were found in the liver and spleen and a single granuloma in the heart of one fish. Transmission electron microscopy (TEM) revealed that the organism was composed of 2 cells, an outer cell enclosing an inner cell. The inner cell was surrounded by a double membrane and the outer cell by a single membrane. Cellular material, presumably of parasitic nature, surrounded the outer cell. The organism contained primitive mitochondria and abundant free ribosomes. Small subunit ribosomal DNA (SSU rDNA) sequence obtained by PCR revealed an 84% sequence identity with the myxosporean Latyspora scomberomori. Based on TEM and preliminary molecular results, we suggest that the organism is the extrasporogonic developmental stage of a myxozoan parasite, which failed to form spores in the mulloway host.     

Pregnancy effects on rat adipose tissue lipolytic capacity are dependent on anatomical location.

Pregnancy is characterized by changes in maternal adiposity. The aim of this study was to carry out a detailed analysis of the different steps of the adrenergic pathway, lipoprotein lipase (LPL) levels and adipocyte size, in order to evaluate the response of white adipose tissue (WAT) to the metabolic changes during pregnancy depending on the anatomical location. In general, the levels of the proteins of the lipolytic pathway decreased with pregnancy. In retroperitoneal WAT adenylate cyclase (AC) levels decreased from 100% in controls to 44% by day 13 and 11% by day 20. In mesenteric WAT the alpha (2A)/beta (3)-adrenergic receptor balance seemed to be one of the main regulatory points of the lipolytic pathway and the reduction in the postreceptor element levels was clearly lower than for the other two depots (PKA levels reduced from 100% in controls to 72% by day 20, while in the other two depots it decreased to 30%, and AC and HSL levels did not show statistically significant changes in this depot). In contrast, the LPL-to-HSL ratio may be a major regulatory point in gonadal WAT. In summary, we describe regional differences in the regulation of WAT metabolism throughout pregnancy, which may be of great importance to determine the role of the different fat depots during late pregnancy. Thus, gonadal and mesenteric WAT changed to a lipolytic state to sustain the rapid foetal growth, although with differences between them in the main regulatory points, while retroperitoneal WAT could have a role later on, during lactation.     

Synopsis of biological, fisheries and aquaculture-related information on mulloway Argyrosomus japonicus (Pisces: Sciaenidae), with particular reference to Australia

Argyrosomus japonicus is a member of the family Sciaenidae, which are commonly known as drums and croakers. A. japonicus occurs in estuarine and nearshore Pacific Ocean and Indian Ocean waters surrounding Australia, Africa, India, Pakistan, China, Korea and Japan. The biology of A. japonicus is relatively well studied in South Africa, and more recently studied in Australia, but no information is readily available from other areas of its distributional range. The early life history distribution of A. japonicus may differ among regions, with their distribution in estuaries linked to salinity, turbidity, freshwater flows and depth of water. Studies in South Africa and Australia found that juvenile fish grow rapidly, attaining 35 cm TL in 1 year and 87–90 cm TL in 5 years. Sexual maturity also differs among regions and is attained at 2–3 years of age and >50 cm in eastern Australia, 5–6 years of age and >80 cm TL in western Australia and southern Africa. The maximum reported length and age of A. japonicus is 175 cm and 42 years, respectively. Spawning most likely occurs in nearshore coastal waters although there is evidence to suggest that it may also occur in the lower reaches of estuaries. Time of spawning varies among geographic localities and is probably linked to water temperature and oceanography. Juvenile fish (<2 years) appear to be relatively sedentary, but sub‐adults and adults can move relatively long distances (>200 km) and such movements may be linked to pre‐spawning migrations. A. japonicus is important in many recreational and commercial fisheries, but like other sciaenids, is prone to overfishing. It is classified as recruitment overfished in South Africa and overfished in eastern Australia. Although much research has been done to minimize the capture of juveniles in Australian prawn‐trawl fisheries, greater protection of spawners and improved fishing practices to enhance survival of discarded juveniles, particularly from prawn trawling, may be required. An aquaculture industry is developing for A. japonicus in Australia and preliminary research on the impacts and success of re‐stocking wild populations has begun in an attempt to arrest the apparent decline in populations.     

The effects of 11-ketotestosterone on occupation of downstream location and seawater in the New Zealand shortfinned eel, Anguilla australis

The androgen 11-ketotestosterone (11KT) is associated with the physiological and morphological changes that occur during the transformation of sedentary ('yellow') freshwater eels (Anguilla spp.) into their migratory form ('silver') prior to their spawning migration in the ocean. In this study, we investigate the possible role of 11KT in modulating behaviors consistent with downstream migration; i.e., downstream and salinity preference in the New Zealand shortfinned eel (A. australis). Unlike silvering, 11KT did not induce preference for downstream locations, scored as presence at the downstream ends of 35 m raceways. Likewise, there was no evidence for increased salinity preference in 11KT-treated yellow eels, scored as preference for sea water over fresh water in a choice experiment. However, the 11KT treatment induced higher frequency of movements between fresh water and sea water, which may indicate restlessness.     

Release of piperonyl butoxide and permethrin from synergized ear tags on cattle and effects on horn fly mortality

A study was conducted to determine the release rates of piperonyl butoxide (PBO) and permethrin from synergized insecticidal cattle ear tags and their effects on mortality of the horn fly, Hematobia irritans irritans (L.) (Diptera: Muscidae). PBO was released from the ear tags at a higher rate than permethrin in both winter and summer trials. The cumulative release of PBO and permethrin from the ear tags at the end of 18 wk in the winter trial was 50.4 and 30.3%, respectively. The cumulative release of PBO and permethrin from the ear tags at the end of 18 wk in the summer trial was 66.7 and 44.7%, respectively. There was a significant correlation between the cumulative daily high ambient temperature (degrees C) and the cumulative release of both PBO and permethrin. Compared with the susceptible horn fly strain, the permethrin-resistant strain demonstrated 7.9- and 12.8-fold resistance to permethrin at the levels of LC50 and LC90, respectively. When exposed to filter paper wipes taken from the shoulders of cattle treated with the PBO-synergized permethrin tags from the summer trial, the resistant strain demonstrated reduced mortality compared with the susceptible strain. The mortality of the resistant strain at 2- and 3-h exposure exhibited a pattern of declining fly mortalities as a result of the decreased release of PBO and permethrin, as well as the decline in the ratio of PBO:permethrin released from the tags after 8 wk. A similar decline in horn fly mortalities was observed in the susceptible strain at 30-min exposure time that coincided with the pattern of reduced release of PBO and permethrin from the ear tags over the course of summer trial.     

The effects of egg position, egg mass size, substrate and biofouling on embryo mortality in the squid Sepioteuthis australis

Using a combination of laboratory and field investigations, this study examined embryo mortality in the southern calamary Sepioteuthis australis as a function of egg mass size, the substrate upon which the mass is attached, the position of the embryo within the mass, and the degree of biofouling. Egg mass size ranged from 2 to 1,241 egg strands, however most masses consisted of 200–299 strands. Small egg masses (<300 strands) were generally attached to soft-sediment vegetation (Amphibolis antarctica, Heterozostera tasmanica, Caulerpa sp.), whereas larger masses (>300 strands) were either securely attached to robust macroalgae holdfasts (Ecklonia sp., Marcocystis pyrifera, Sargassum sp.) or unattached. Rates of embryo mortality were highly variable ranging from 2 to 25%. Both laboratory and field results indicated a positive relationship between egg mass size and embryo mortality. Larger, unattached egg masses contained twice as many dead embryos than those securely attached to a substrate. Mortality rates were significantly affected by the embryos’ relative position within the mass and were highest in embryos located near the attachment point of the egg strand, within the interior of the mass, and in close contact with the substrate. This was attributed to the inability of the embryos to respire adequately and eliminate metabolic wastes. Biofouling did not strongly influence embryo mortality, but colonisation occurred in areas conducive to growth, photosynthesis, and respiration indicating ‘healthy’ regions within the mass.     

Factors affecting early mortality in the South American fur seal (Arctocephalus australis) in Peru: density-related effects and predation

Early mortality in the South American fur seal ( Arctocephatus australis ) in Peru is considerably higher than that seen in any other population of fur seal; 31–49% in the first month as opposed to a maximum of 20% in other populations. In 1987 and 1988, pup mortality was found to be enhanced by density-related effects and predation on pups by the southern sea-lion ( Olaria byronia ). At a high density beach, where 60% of the fur seals bred, mortality correlated with the number of females ashore as did aggression. Female aggression was driven to high levels by a combination of high density and movement within the colony to thermoregulate. However, even at a low density, beach mortality remained high due to a high level of predation by male southern sea-lions (low density beach 5·0–8·3% of all pups; high density beach 0·2%). Predation rates were lower at the high density beach because male fur seals expelled most attacking sea-lions during the breeding season (low density beach 10·0% of attacking sea-lions expelled; high density beach 58·8%).     

Spawning period and growth of yellowfin bream, Acanthopagrus australis (Günther), in Moreton Bay, Australia

Monthly changes in the gonosomatic index indicate that yellowfin bream, Acanthopagrus australis , in Moreton Bay have a short spawning season with a peak during the period July to August each year. The growth rate of A. australis was estimated from tag-recapture data and by length-frequency analysis. Modes representing age classes 0, I and II often appeared in length-frequency distributions, however modes for older age classes were difficult to identify. The von Bertalanffy growth curve parameters calculated from release–recapture data are: L_∞ = 29.5 cm; K = 0.51; t ₀=– 0.32 years.     

Damage, recovery and survival of 0-group mulloway, Argyrosomus japonicus, after simulated escape through square mesh

A laboratory experiment was carried out to quantify and compare the physical damage (measured as scale loss), recovery and survival of two size categories [small: 48–85 mm total length (TL); large: 78–148 mm TL] of 0‐group mulloway, Argyrosomus japonicus, after simulated escape through square‐shaped mesh (bar length of 21.5 mm). Regardless of their size, fish that were fatigued to exhaustion and forced through square meshes sustained significantly more (i.e. >1.8 times) scale loss than did control fish that were only fatigued. However, the total scale loss incurred was <5% and significantly improved 7 days after treatment. Survival rates over a 2‐week observation period were 100 and >97% for treatment and control fish, respectively. The results support the utility of square mesh for reducing the prawn‐trawl fishing mortality of unwanted bycatch.     

Themeda australis grasslands on the Basalt Plains,Victoria: floristics and management effects

The floristic composition of remnants ofThemeda australis grasslands from basaltic areas of western Victoria was described using methods employed by the Zürich-Montpellier school of phytosociology. Most sites sampled were managed by either regular burning (rail sites) or grazing, or were not subject to any regular management practices (roadside sites). Rail sites contained relatively open, species-rich vegetation with a smaller proportion of introduced species than the other two types of site. Grazed paddock sites contained relatively open, species-poor vegetation, whilst roadside sites contained relatively dense, species-poor vegetation. Such site differences appear to be related to the effect of management practices upon the competitive ability of T. australis and to species tolerance of them.     

Effect of cell size, age and anatomical location on the lipolytic response of adipocytes

Studies were conducted on the norepinephrine (NE) stimulated lipolytic sensitivity of adipocytes from epididymal (Epi), perirenal (PR), subcutaneous (SC) and mesentric (M) depots from young (7–8 wk.) and adult (14–16 wk.) male rats. In the young rats dose response curves to NE were similar for Epi, PR and M depots whereas adipocytes from the SC depot showed a diminished effect over the mid-portion of the curve. This difference could not be ascribed to differences in cell size. In the adult rats glycerol release in the Epi depot in response to NE was identical to the younger rats which was in marked contrast to the other depots in which glycerol release was decreased in comparison to the younger animals. This decreased responsiveness was probably largely a result of age and not changes vn adipocyte size within a given depot. In these older rats, glycerol release was greatest in the Epi cells, least in the SC and M depots, and intermediate in PR. When young rats were subjected to a 72-hour fast, loss of triglyceride per cell was the same in all depots as predicted by the $\text{in vitro}$ data whereas in old rats (610 g), triglyceride loss was proportional to cell size with Epi ≥ PR > SC ≥ M. This was also essentially in agreement with the $\text{in vitro}$ lipolytic data from adult rats. These data demonstrate lipolytic differences between depots that are minimal in young rats and which are accentuated with age.     

Isolation and characterization of 15 polymorphic microsatellite DNA loci from Argyrosomus japonicus (mulloway), a new aquaculture species in Australia

Fifteen microsatellite loci were isolated for population genetic studies of mulloway (Argyrosomus japonicus), a commercial/recreational fish species in Southern Australia. A genomic library was screened randomly for di- tri- and tetranucleotide repeats. Fifteen microsatellite marker loci were developed that were highly polymorphic (allele number ranged from four to 18). Observed and expected heterozygosities ranged from 0.17 to 1 and from 0.27 to 0.91, respectively. These markers have proven useful for estimating genetic variation and for evaluating population structure across the species' natural distribution. They also provide powerful tools for optimizing hatchery practices to conserve genetic diversity.     

Effect of short term exposure to the anaesthetic 2-phenoxyethanol on plasma osmolality of juvenile dusky kob, Argyrosomus japonicus (Sciaenidae)

The plasma osmolality of early juvenile dusky kob, Argyrosomus japonicus , exposed to 2-phenoxyethanol and control fish that were pithed prior to sampling, was investigated. Exposure to 2-phenoxyethanol, after 2, 4, 6, 8 and 10 min, did not alter plasma osmolality (Friedman test; P = 0.976). There was no significant relationship between the size of fish within the range 133–170 mm SL (40–85 g) and plasma osmolality. Finally, there was no significant difference in plasma osmolality between anaesthetized fish and the control group that were pithed directly after removal from the tanks. Anaesthetizing juvenile dusky kob with 2-phenoxyethanol prior to blood sampling did not affect plasma osmolality.