An assessment of the angling fishery for yellowfin bream, Acanthopagrus australis (Günther), in Moreton Bay, Australia

Yellowfin bream, Acanthopagrus australis , support an important angling fishery in Moreton Bay, a large estuarine system on the east coast of Australia. An analysis of the records of catches by anglers indicates that abundance and mean size of yellowfin bream have changed little in Moreton Bay during the period 1945 to 1980. Over the past 5 years substantial increases have occurred in the total angling effort for yellowfin bream at surf bar spawning areas in Moreton Bay. This has resulted in a decrease in mean catch per unit effort but no apparent decrease in total yield. Reclamation and development projects which cause degradation of the surf bar spawning areas have the greatest potential to cause reduction in abundance of yellowfin bream in Moreton Bay.     

Movements and migrations of yellowfin bream, Acanthopagrus australis (Günther), in Moreton Bay, Queensland as determined by tag recoveries

Yellowfin bream were tagged and released in three non-spawning areas and two spawning areas in Moreton Bay, a large estuarine system on the east coast of Australia. A total of 194 fish were recaptured. Juvenile fish made only small-scale movements (less than 6 km) from the release site. Small-scale movements were also recorded for adult fish, although large-scale movements from 10 to 90 km were also recorded. The large-scale movements appear to be associated with the migration of adult fish to or from surf bar spawning areas. Some adult fish remained in feeding areas during the spawning season (May-August). There was no indication from tag recoveries of any movements of yellowfin bream outside Moreton Bay and the results indicate that adult yellowfin bream in Moreton Bay may be regarded as a unit stock for the purpose of fisheries management.     

Recruitment and growth of juvenile yellowfin bream, Acanthopagrus australis Günther (Sparidae), in an Australian intermittently open estuary

Recruitment and growth of juvenile yellowfin bream, Acanthopagrus australis Günther (Sparidae), an economically important species, were examined in an intermittently open Australian estuary for 13 months. Fish had a mean fork length of 77.9 (± SE 9.5) mm after 1 year. Growth rates were faster than those found in previous studies in permanently open estuaries and appeared to be dependent upon the water temperature, which ranged from 0.04 mm/day in winter to 0.67 mm/day during summer. However, periods of slower growth may also reflect the emigration of larger fish from the cohort when the estuary was open and which coincided with lower water temperatures. Growth and length-at-age of fish using length-frequency data may be estimated more accurately in intermittently open estuaries because the time of recruitment can be determined, especially when the estuary opening period is short.     

Saddleback syndrome in yellowfin bream [Acanthopagrus australis (Günther, 1859)] in Moreton Bay,Australia: its form,occurrence, association with other abnormalities and cause

The aim of this study was to determine if saddleback syndrome (SBS) in a wild population of yellowfin bream (Acanthopagrus australis) was the result of a developmental defect or caused by physical injury. Information was collected in 2012 on the incidence of SBS and other abnormalities in this species in Moreton Bay, Australia. Abnormalities in adult fish (>250 mm Total Length, TL) with SBS (n = 47) were compared with those without SBS (n = 30). A sample of juvenile fish (n = 404) was checked for the presence of SBS. The results show that scale loss, scale pattern misalignment, lateral line fracture and pectoral fin abnormality were closely associated with SBS. SBS was uncommon (<2%) in juveniles <70 mm TL, but common (>12%) in the larger juveniles (70–215 mm TL). These results, together with the findings that scale loss associated with SBS in adult fish occurred in the range 80–245 mm back‐calculated TL, indicate that SBS and the related abnormalities in yellowfin bream are a result of physical injuries to larger juveniles (>70 mm TL). The reduction in the incidence of SBS from approximately 12% in the larger juveniles to 5% in adults is evidence of mortality associated with SBS.     

The reproductive cycle of yellowfin bream, Acanthopagms australis (Günther), with particular reference to protandrous sex inversion

Yellowfin bream, Acanthopagrus australis , of all age classes were collected from Moreton Bay, Australia. The species possessed typical sparid ovotestes in which the testis and ovary occur in separate zones. During the spawning period (June-August) juveniles, functional males and functional females could be distinguished by the macroscopic appearance of the gonad. The sex ratio of males to females decreases with age, indicating protandrous sex inversion.
Histological and structural study of the ovotestis showed all fish have previtellogenic cells in the ovarian zone but only juvenile and male fish have developing spermatogenic cells in the testis. Most juveniles become functional males by the age of two years but a small proportion of juveniles develop directly into functional females (primary females). Protandrous sex inversion commences after the spawning period when male fish appear with spermatozoa and no other spermatogenic cells in the testis. During the period November-January male fish with no spermatogenic cells are common and a reduction in size of the testis occurs so that by March-April the ovotestis becomes structurally and histologically similar to the female ovotestis. Some fish remain functional males during their whole life-history (primary males). In functional females vitellogenic cells are present in the ovary only during the spawning period and the testis remains very small in size.     

Blood and other possible inflammatory cells in the sparid Acanthopagrus australis (Günther)

The peripheral blood cells of Acanthopagrus australis include erythrocytes, elongated and rounded thrombocytes, lymphocytes, neutrophils and monocytes. The ultrastructure of lymphocytes, neutrophils and monocytes is described. Type 1 cells with characteristic elongated, eosinophilic granules and type 2 cells with rounded, apparently labile granules are common in the gill filaments and do not increase or decrease significantly in abundance in ectoparasite-infested gill filaments. Extravascular neutrophils tend to be more evident in pathologic tissue. Lymphocytes and the macrophage-like type 3 cells are the most abundant infiltrating cells in pathologic gill tissue. Apart from ultrastructural and histochemical data, granule length and width are sufficient criteria to distinguish between the neutrophil, type 1, type 2 and type 3 cells.     

The seasonal occurrence of postlarval stages of yellowfin bream, Acanthopagrus australis (Gunther), and some factors affecting their movement into an estuary

Planktonic postlarvae of yellow fin bream Acanthopagrus australis were found at surf bar entrances to Moreton Bay, a large subtropical estuarine system on the east coast of Australia. The postlarvae occurred from April to September with peak abundance during July to September. Most postlarvae entered the estuary at night during the full moon. They were more abundant on the flood and full tides than on the ebb tide. The transition from planktonic to littoral existence occurs from August to November when the fish are 13-14 mm in length. Young yellow fin bream in littoral areas reach a modal length in excess of 100 mm after 1 year.     

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.     

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.     

Age determination and growth of luderick, Girella tricuspidata (Quoy and Gaimard), taken from Moreton Bay, Australia

Age and growth patterns of luderick, Girella tricuspidata (Quoy and Gaimard), taken in the Moreton Bay net fishery are described. Scales have prominent annuli which are formed during the period May-July. The mean body length is similar for males and females, except for age class III where female fish are significantly larger. This probably results from the early movement of faster growing females onto the fishing ground. The scale method and length-frequency analysis both indicate that the variation in body lengths in each age class is large. The length-weight relationship was obtained and relative condition factor was found to be highest in July which corresponded with the peak in gonosomatic index.     

The growth of charr, Salvelinus willughbii Günther, in Windermere

The growth of charr ( Salvelinus willughbii Günther ) caught in Windermere from 1941–1952 has been studied. Scales were used for determination of age and back-calculation of length for age. Autumn and spring spawners, males and females, and charr of normal and dwarf growth were treated separately. In fish of normal growth, the spring spawners were significantly smaller than the autumn spawners at ages 1 and 2 years, and significantly larger from age 4 years onwards. There was little difference in growth between males and females within the two spawning populations. Charr of lengths of less than 200 mm at age 4 years were considered to be dwarfs. Mean lengths at capture of male charr were: autumn spawners normal growth 272 mm, dwarf 218 mm; spring spawners normal growth 327 mm, dwarf 194 mm. The oldest recorded age was 8 years.     

Age, growth and reproduction of the barbel, Barbus sclateri (Günther, 1868), in a first-order stream in southern Spain

This study was based on examination of 1476 barbels from a first-order stream located in the Guadalquivir River basin (38°N, 4°43'W). This stock comprised nine age groups of male and 11 of females. No growth was recorded between October and March, most occurring in April–June and, to a lesser extent, in July–September. A classification analysis revealed that this stock had the lowest growth rate of 37 different European barbel populations. Length–weight relationships were obtained for 12 barbel categories and used to estimate both condition and instantaneous growth rate. Relative condition (before and after subtracting gonad weight) was similar in both sexes and was affected by gonad growth and environmental summer conditions.
Spawning occurred during the second half of May (15 May is suggested as the birthday). Gonads began to develop in September (females) and in February (males). Males matured at between 7 and 9 cm fork length (f.l.) (2–4 years old) and females between 11 and 16 cm (6–7 years). The fecundity of this stock was represented by the formula F =6.07 10 ⁴ f.l. (mm)^3.0667. Larger and older fish showed a higher fecundity and bigger eggs. The overall sex ratio did not differ from 1:1.     

Cardio-respiratory morphometrics of spangled perch, Leiopotherapon unicolor (Günther, 1859), (Percoidei, Teraponidae)

The heart of Leiopotherapon unicolor comprises 0.135±0.005% of total body weight compared to the average teleost heart size of 0.081±0.002% body weight. The respiratory surface area of 569 mm² g⁻¹ is also much larger than that found in most freshwater fish. The exponent b in the equation Gill Area = a. body wt^b was evaluated at 1.04, whereas the theoretical value for b is only 0.75. It is therefore evident that L. unicolor has an excessively large gill area and a large heart, which facilitate oxygen uptake in hypoxic environments.     

Fine-scale genetic structure derived from stocking black sea bream, Acanthopagrus schlegelii (Bleeker, 1854), in Hiroshima Bay, Japan

Black sea bream ( Acanthopagrus schlegelii ) is an important commercial and sport fishing species inhabiting Hiroshima Bay, where an intensive stock enhancement program is carried out for this species. In order to clarify the fine-scale genetic effects of the releases, black sea bream specimens were collected at five locations (Ninoshima, Atatajima, Miyajima, Oonasamijima and Kurahashi) in Hiroshima Bay. High homogeneity was observed among locations. The sample from Ninoshima, where stocking was most intense, presented the lowest number of alleles per locus (13.5) and showed significant differences in the pairwise F _ST value compared to the fish at Atatajima, Miyajima and Oonasamijima, but not significantly different from those collected at Kurahashi. However, all differences disappeared once analysis was performed standardizing the age-classes of all samples. The results suggest an important effect of the releases on genetic diversity of A. schlegelii in Hiroshima Bay. Moreover, the observed genetic population substructure is presumed to be related to the year-class composition of the samples at each location.     

An anomalous specimen of Rhamdia guatemalensis (Günther, 1864)

In March of 1984 an immature Rhamida guatemalensis (Günther, 1864) lacking the right pectoral fin (Fig. 1) was captured in the Sangregado sector, Arenal Dam, Guanacaste, Costa Rica (10°28' N, 84°46'W) The body colouration and morphometric characteristics were as described for this species (Bussing 1966; Zúñga, 1980). X-ray examination revealed the absence of the radial bones and the fin rays of the right peoctoral fin. External examination of the tegument of this region showed no scars or evidence of accidental loss of the appendage, indicating that the fin had never developed.
Morphometric data from this abnormal specimen are: total length, 14.25 cm, standard length, 11.98cm; maximum height of body, 22.35 cm; maximum width of body, 2.40 cm, caudal peduncle width, 1.27 cm; head length, 3.00cm.     

Community structure of soft sediment pool fishes in Moreton Bay, Australia

A survey of soft sediment tide pools was conducted to assess the occupation and assemblage of fishes on three different intertidal shores in Moreton Bay, Australia, between January and December 2009. Tide-pool volume ranged from 0· 30 to 29· 75 l and varied significantly between months and sites. A total of 1364 individuals representing 15 species and nine families of fishes were observed. At Dunwich, fish assemblages were dominated by the sand goby Favonigobius lentiginosus (89%) and whiting, Sillago spp. (10%). At Manly, the gobies Favonigobius exquisitus (37%), Pseudogobius sp. (31%) and the blenny Omobranchus punctatus (19%) dominated the shores while at Godwin Beach, F. lentiginosus (15%), F. exquisitus (45%) and Sillago spp. (25%) were the most abundant species. The mean ±s.e. density of fishes ranged from 0· 29 ± 0· 13 to 5· 04 ± 1· 74 fishes l(-1) and abundance of fish correlated with pool volume. Juveniles (75%) dominated assemblages suggesting that soft sediment pools may act as nurseries. The persistent and recurrent fish assemblages found in soft sediment tide pools in Moreton Bay suggest that these shores are behaving more like a tropical than a temperate climate shore, as there was no significant difference of fish abundances between seasons.     

The routine metabolism of the guapote, Cichlasoma managuense (Günther 1869), related to body weight and temperature

The routine metabolism of the guapote tigre, Cichlasoma managuense , was measured for a weight range between 6 mg and 800 g and at three different temperatures: 22, 27 and 32° C. Equations describing the routine metabolism of the guapote in relation to fish weight and temperature were calculated. The results are compared with those of other stenothermal tropical species.     

Habitat and resource partitioning among Indo‐Pacific bottlenose dolphins in Moreton Bay,Australia

Investigating resource partitioning among mobile marine predators such as cetaceans is challenging. Here we integrate multiple methodologies (analyses of habitat use, stable isotopes and trace elements) to assess ecological niche partitioning amongst two genetically divergent sympatric subpopulations (North and South) of Indo‐Pacific bottlenose dolphins (Tursiops aduncus) in Moreton Bay, Australia. Comparisons of the mean locations (latitude, longitude) and environmental variables (distance from sandbanks, distance from shore and water depth) observed at sightings of biopsy‐sampled individuals indicated that the North subpopulation occurred in the northwestern bay in significantly deeper water than the South subpopulation, which was found in southeastern nearshore waters and closer to sandbanks. Ratios of stable carbon and nitrogen isotopes in skin samples suggested that North dolphins foraged on higher trophic level prey in relatively more pelagic, offshore habitats, while South dolphins foraged on lower trophic prey in more nearshore, demersal and/or benthic habitats. Habitat partitioning was also reflected in higher blubber concentrations of most of the 13 measured trace elements, in particular lead, in the coastal South compared to the more pelagic North dolphins. These findings indicate that genetic subpopulations of bottlenose dolphins in Moreton Bay are adapted to different niches.     

Metabolic enzyme activities in black bream (Acanthopagrus butcheri) from the Swan-Canning Estuary, Western Australia

The Swan-Canning estuary, in southwestern Australia, is subject to frequent algal blooms and associated periods of hypoxia due to high levels of nutrients in stormwater runoff and sewage spills. Fish in which cellular respiration is impaired due to chronic exposure to non-nutrient pollutants in the water will have a reduced ability to survive these periods of high stress. In order to investigate if metabolic respiration in black bream (Acanthopagrus butcheri) was altered, fish were collected from five sites in the Swan-Canning estuary in summer 2001, summer 2002 and winter 2002. Aerobic and anaerobic capacities were estimated by measuring the enzymes cytochrome C oxidase (CCO) and lactate dehydrogenase (LDH). Neither seasonal or annual trends, nor upstream or downstream gradients were observed in either biomarker. The fish collected from the Barrack Street site, which is close to the Perth Central Business District, were heavily challenged in their aerobic capacity in the summer months compared to the other sites. In addition, the fish at Barrack Street displayed an altered anaerobic capacity. It is likely that the impaired metabolic capacity of the fish at Barrack Street reduces the fishes' ability to survive the frequent algal blooms within the estuary.