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.     

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.     

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.     

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.     

Further studies on the sexuality of the hermaphroditic teleost Diplodus sargus, with particular reference to protandrous sex inversion

Histological events associated with the process of sex inversion are described in the protandrous teleost Diplodus sargus reared in captivity. This species possesses typical sparid ovotestes in which the testis and ovary occur in separate zones. After spawning, the testicular tissue within the bisexual gonad undergoes regressive changes such as spermatogonial degeneration, deposition of yellowish pigment and proliferation of connective cells and fibres. At the same time ovarian tissue begins to develop. Transitional individuals were 26–7% of examined fish, while the other 73–3% were functional males.     

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 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.     

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.     

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.     

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.     

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.     

Olfactory responses to steroids in an African mouth-brooding cichlid, Haplochromis burtoni(Günther)

Underwater electro‐olfactogram (EOG) recordings involving 150 steroids and eight prostaglandins were used to determine which of these potential odorants are detected by the olfactory organ of an African cichlid, Haplochromis burtoni. In initial EOG tests at 10^?9 M, H. burtoni did not respond to unconjugated steroids or prostaglandins, but did respond to 17 conjugated steroids, 11 of which (17β‐oestradiol‐17β‐glucuronide; 17β‐oestradiol‐3‐sulphate; 17β‐oestradiol‐3,17β‐disulphate; epiandrosteron‐3β‐sulphate; etiocholanolone‐3α‐glucuronide; testosterone‐17β‐sulphate; dehydroepiandrosterone‐3β‐sulphate; 5α‐pregnan‐3β‐ol‐20‐one‐3β‐sulphate; 5β‐pregnan‐3α,17‐diol‐20‐one‐3α‐glucuronide; 5β‐pregnan‐3α,17,21‐triol‐11,20‐dione‐3α‐glucuronide; pregnenolone‐3β‐sulphate) were selected for EOG concentration‐response, cross‐adaptation and binary mixture tests. The EOG detection thresholds ranged from 10^?11 to 10^?9 M in all but one instance (female threshold to pregnenolone‐3β‐sulphate; 10^?8 M), and males and females exhibited only minor differences in EOG threshold or response magnitude. Results of EOG cross‐adaptation tests, which were supported by results of binary mixture tests, indicated that the response to the 11 steroid conjugates is mediated by five putative olfactory receptor mechanisms characterized by specificity for conjugate position and type: 3‐sulphate, 17‐sulphate, 3,17‐disulphate, 3‐glucuronide, 17‐glucuronide. Although there is no evidence that H. burtoni releases, or exhibits biological response to, the steroids shown to be detected in this study, the present results are suggestive of a complex pheromone system utilizing steroid conjugates.     

Some ultrastructural features of Volvox,with particular reference to the phenomenon of inversion

Summary Some features of the ultrastructure of Volvox are described. Golgi bodies were often associated with the endoplasmic reticulum (ER), and the two basal bodies appeared to be accompanied by two probasal bodies. A few vegetative cells were binucleate. All cells examined had a peripheral cytoskeleton of microtubules which was particularly well developed in the cells of sperm packets. During inversion of a colony, the cells elongated considerably, possibly due to the increased length of these peripheral microtubules; the cell profile also became some-what narrowed at the inner edge of the flexing colony. Cytoplasmic connections were large and numerous in young coenobia, but were generally absent in older vegetative colonies; by inversion, they had become confined to the chloroplast end of the cells where they seemed to act as hinges. Elements of the ER ran through these interconnections, possibly providing an intercellular communication network needed for the coordinated activity of inversion. A new structural feature was discovered in the form of circular (or possibly spiral) striations on the plasmalemma around these cytoplasmic connections. They were detectable just before inversion, and were most pronounced immediately after.     

The oestrous cycle with particular reference to the neural control of the ovary

The differing types of oestrous cycle found in mammals seem to be manifestations of the degree to which the external environment participates in the control of the three main phases of the ovarian cycle, the follicular phase, ovulation, corpus luteum phase. The question of the importance of the external and the internal environment for the manifestations of cyclicity has been discussed by reference to the factors involved in the control of ovarian function. The control of the ovarian cycle involves an interrelated fluctuation in the secretion of the anterior pituitary gonadotrophins FSH and LH, and in certain species LTH, which are under the control of hypophysiotrophic hormones produced in the hypothalamus. The production of these hormones is modified by other hypothalamic and extra–hypothalamic mechanisms, including a probable preoptic cycling mechanism controlling the ovulatory surge of gonadotrophins. These mechanisms can be triggered and timed by means of nervous reflexes arising from a variety of sensory end organs. Also this brain–hypothalamus–pituitary unit appears to contain sex steroid and gonadotropin sensitive elements through which these factors can influence the system. The additional luteotrophin and luteolytic factors involved in corpus luteum control have not been discussed. A brief idea as to how all these factors are integrated for the control of ovarian cyclicity is presented.     

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.     

A new species of Creagrutus Günther (Teleostei: Ostariophysi: Characiformes), from the upper Rio Paraná basin, central Brazil

Creagrutus varii n. sp. is described based on material from the Rio São Marcos basin, in the upper Rio Paraná system, Goiás State, Brazil. This is the first record of Creagrutus in the upper Rio Paraná. The new species is proposed to be the sister group of the remaining species of Creagrutus . Creagrutus varii differs from congeners in the morphology of the maxilla, primordial ligament, premaxillary dentition and other features. The evolution of premaxillary tooth morphology in Piabina and Creagrutus and the biogeography of the Rio Paranaíba basin are discussed.     

Influence of gut morphology, sensory cues and hunger on feeding behaviour of spangled perch, Leiopotherapon unicolor (Günther, 1859), (Percoidei, Teraponidae)

The morphology of the alimentary canal, feeding technique and responses to sensory cues were investigated in Leiopotherapon unicolor . The small conical teeth on the jaws and pharynx, simple Y-shaped stomach and short gut of L. unicolor are characteristic of opportunistic carnivorous fish. Five types of behaviour, 'basal', 'orientation', 'positioning', 'attack', and 'ingestion', were recognised and are described. Capture of prey small enough to swallow whole was assisted by suction created as the mouth opened to engulf prey. Crustaceans too large to ingest whole were broken into smaller pieces against the substrate. Directional and oscillatory movement were the most effective sensory cues in eliciting feeding behaviour, implicating vision as an important sense for L. unicolor feeding in confined aquaria. Acoustic and olfactory senses are less important in prey capture. The frequency with which spangled perch responded to different sensory cues increased with increasing hunger.