Pharmacological and histological assessment of gut muscle movement in blacklip abalone, Haliotis rubra (Leach)

We examined the basic pharmacology of abalone gut tissues for adrenergic and peptide receptors using ligand binding and by determining the pharmacological effectors of abalone gut motility in a number of gut regions. Contractile responses could not be elicited, even though we could show the existence of α‐adrenergic and peptide receptors. Responses to any muscle contractile agents, including carbachol and potassium chloride, could not be found in blacklip abalone, Haliotis rubra (Leach). Histology confirmed the relative absence of muscular layers in all the tissues of the gut, indicating that previous literature reports of muscular involvement in contractile movement of gut contents did not appear to apply to this species.     

Anti-Müllerian Hormone as a Diagnostic Marker for Equine Cryptorchidism in Three Cases with Equivocal Testosterone Concentrations

Cryptorchidism is a developmental disorder which can be diagnosed by a variety of different tests. Still, equine field veterinarians often rely on endocrine markers to detect retained testicular tissue. This report describes the value of anti-Müllerian hormone (AMH) as a diagnostic marker for cryptorchidism in three stallions suspected of cryptorchidism, with equivalent serum testosterone concentrations. A single measurement of AMH identified cryptorchidism, with inconclusive testosterone concentrations as either gelding or stallion. Furthermore, a human chorionic gonadotropin (hCG) stimulation test or surgery was performed to support the diagnostic value of AMH. To conclude, the endocrine panel for cryptorchidism should be expanded to include determination of serum AMH, as this determination can increase the diagnostic accuracy of a single blood sample.     

A test of the individual feeding activity and food size preference in rainbow trout using demand feeders

Feeding activity and food size preferences were investigated in three groups of rainbow trout with initial weights ranging from 200 to 1000 g. Fish were given the option of releasing food from either of two demand feeding devices that contained either 6 mm or 9 mm food pellets. Individual biting activity (to activate release of food) was continuously monitored using specially designed passive integrated transponders (PIT-tags). In each of the groups, biting activity was strongly influenced by three individuals, which accounted for 70–85% of the total. Thus, high bite activity by few individuals indicates the development of social dominance hierarchies. There was no statistically significant correlation between number of bites and growth rate, indicating that the fish that operated the demand feeders did not gain any growth advantage. Trout that dominated the actuation of the feeders were found among both medium- and large-sized fish. There was no evidence of active food size selection, and the fish that most frequently operated the feeders defended one area of the tank rather than preferring the trigger that would have delivered food of the optimal size.     

Testing a depth‐based Habitat Classification System against reef fish assemblage patterns in a subtropical marine park

• 1. The Solitary Islands Marine Park (SIMP) in New South Wales (NSW), Australia, has strong cross‐shelf patterns of reef fish assemblages on shallow reefs (<25 m). While the SIMP also contains reef at depths of up to 75 m, marine communities below 25 m are poorly described. The Habitat Classification System (HCS) used for planning the arrangement of zones in this marine park included three depth categories for reef: shallow (<25 m); intermediate (25–60 m); and deep (>60 m). However, these had not been tested to determine if they adequately reflect biotic patterns.
• 2. Using baited remote underwater video (BRUV), fish assemblages were surveyed at 56 sites spread across shallow, intermediate, and deep reefs within the SIMP to examine spatial variation between depth categories. Relationships between assemblage patterns, depth, and four additional factors considered likely to affect assemblage patterns (distance from shore, reef type, dominant benthos, and latitude), were subsequently explored using multivariate statistical methods.
• 3. Reef fish assemblages differed significantly among the depth categories. Assemblage patterns for fish were strongly correlated with depth and moderately correlated with the dominant benthic assemblage. Correlations with the other factors were generally weak. Three distinct assemblages occurred on reefs <25 m, 25–50 m and >50 m. Shallow (<25 m) reefs also displayed strong cross‐shelf patterns, supporting the results from other studies. Weaker cross‐shelf patterns were evident at intermediate depths (25–50 m).
• 4. Depth‐based and cross‐shelf categories are clearly fundamental components for a HCS that will adequately represent reef fish assemblages for conservation planning in the SIMP. Further refining the depth criteria for the intermediate/deep boundary (to 50 m) improves this representation. Further research is required to determine the wider application of the refined HCS to other marine parks in NSW and to determine how well it represents other components of biodiversity. Copyright © 2011 John Wiley & Sons, Ltd.

     

The effect of temperature on the clearance of intraperitoneally-injected gonadotropin in the goldfish Carassius auratus

The serum half-disappearance time ($\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$), metabolic clearance rate and volume of distribution of intraperitoneally administered carp gonadotropin (cGtH) and endogenous GtH levels were determined in sexually mature male and female goldfish, Carassius auratus maintained at 12 ± 1°C or 20 ± 1°C. The results indicated that the rate of serum uptake of the injected cGtH from the peritoneal cavity was greater at 20°C than at 12°C in sexually mature male goldfish. Although increased endogenous serum GtH levels and decreased values of serum $\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ were associated with the elevated temperature, there was no difference in any of the parameters between sexually mature male and female goldfish acclimated to 12°C.     

Genetic covariation in production traits of sub-adult black bream Acanthopagrus butcheri after grow-out

Predicting the suitability and reliability of traits associated with juvenile growth as indirect selection criteria for choosing future broodstock requires accurate and repeatable estimates of genetic (co)variation for growth traits at different ages. We compared juvenile wet weight of black bream Acanthopagrus butcheri (Munro) at 6 months of age with wet weight, dressed weight, fillet yield and gonad weight in tagged individuals at 18 months of age, following 12 months of farm grow‐out. Fish survival and tag retention was high, and there was significant among‐family variation for all traits. The phenotypic correlations among wet weight, dressed weight and fillet yield at 18 months of age were very high (0.93–0.97) and similar to their genetic correlations (0.96). Importantly, the phenotypic correlations between wet weight at 6 months and wet weight, dressed weight and fillet yield at 18 months were high (0.63–0.65), and so too were their genetic correlations (0.66–0.73), indicating the potential for using wet weight in the hatchery as a selection criterion for improved weight and meat yield of fish at harvest. Gonad weight shared little or no phenotypic or genetic correlation with these other traits, suggesting that selection for faster growing fish will not affect fecundity or sexual maturation rate. It appears, however, that cultured black bream do become sexually mature more rapidly than wild fish, as 78% of all fish harvested in this study had developing or mature gonads, whereas less than 50% of fish in wild populations are reproductively mature by the same age. Precocious sexual development may lead to uncontrolled spawning in grow‐out ponds and a potential loss of selection gains.     

The Use of Anglers'Returns in the Estimation of Fishing Success

The method of collation of angling results at Ffestiniog fishery is described. Rod averages calculated from returns are always higher than those assessed by the fishery bailiff. Two studies indicated that, although there is no reason to question the veracity of returns, those received represent a sample of anglers which is biased towards the more successful. The care needed in extrapolation from angling returns is emphasized and it is demonstrated that only the bailiff's estimates of fishing success lead to sensible estimates of the seasonal catch.     

Tests of Some Batch-Marking Techniques for Rainbow Trout (Salmo gairdneri Richardson)

Freeze-branding and tattooing by Panjet were used as techniques for rapid application of batch marks to rainbow trout of stockable size. The subsequent performances of the marks produced were compared. Freeze brands took 2 weeks to become clear and thereafter remained wholly satisfactory for only 1 month. Pigments injected by Panjet were immediately visible but of the dyes tested only Alcian blue remained completely clear after a 3-month trial. These results are contrasted with those of other workers in trials with various species of freshwater fish.