Sublethal effects of angling and release on golden perch Macquaria ambigua: implications for reproduction and fish health.

The present study tested the hypothesis of no delayed sublethal effects of mild angling and release on the feeding, growth, somatic condition and gonadal development of golden perch Macquaria ambigua during gametogenesis. Subsamples of adult M. ambigua (n = 17-21 of 207), originally captured from the wild and stocked into ten 0·1 ha earthen ponds, were angled and released during early and late gametogenesis. Wild samples that were concurrently collected throughout the experiment underwent rapid and synchronous gonadal development and many spawned. While no spawning occurred in the ponds, most M. ambigua underwent normal gonadal development to maturity, including the angled fish. Angled fish also fed, maintained condition and actually grew faster than non-angled captive controls. Although females that were angled during late gametogenesis more readily ingested and retained baited hooks, neither their subsequent condition nor gonadal development was significantly affected. The predominance of null results was attributed to the combined effects of the flexible reproductive strategy of M. ambigua, the benignness of mouth hooking and immediate release, and possible methodological issues arising from differential hooking success of more aggressive and resilient individuals. The findings support earlier catch-and-release research, but contrast with reports of acute reproductive effects following capture and handling for aquaculture broodstock. This discrepancy highlights the need for research to specifically address welfare questions relevant to recreational fisheries across various species and angling scenarios.

Mapping the spatio-temporal distribution of threatened batoids to improve conservation in a subtropical estuary.

The spatio-temporal distributions of four batoid species were examined in a subtropical estuary. Fluvial gradient was the most important factor explaining abundances, reflecting positive relationships with either salinity or distance from urbanised areas that were consistent across seasons and depths. The results support existing protected areas.

A one-step-ahead pseudo-DIC for comparison of Bayesian state-space models.

In the context of state-space modeling, conventional usage of the deviance information criterion (DIC) evaluates the ability of the model to predict an observation at time t given the underlying state at time t. Motivated by the failure of conventional DIC to clearly choose between competing multivariate nonlinear Bayesian state-space models for coho salmon population dynamics, and the computational challenge of alternatives, this work proposes a one-step-ahead DIC, DICp, where prediction is conditional on the state at the previous time point. Simulations revealed that DICp worked well for choosing between state-space models with different process or observation equations. In contrast, conventional DIC could be grossly misleading, with a strong preference for the wrong model. This can be explained by its failure to account for inflated estimates of process error arising from the model mis-specification. DICp is not based on a true conditional likelihood, but is shown to have interpretation as a pseudo-DIC in which the compensatory behavior of the inflated process errors is eliminated. It can be easily calculated using the DIC monitors within popular BUGS software when the process and observation equations are conjugate. The improved performance of DICp is demonstrated by application to the multi-stage modeling of coho salmon abundance in Lobster Creek, Oregon.

Failure to demonstrate high concentrations of luteinising hormone-releasing hormone in the bovine pineal body.

Six in vitro experiments were conducted to study the effects of the incorporation into the culture system of 10 bovine pineal bodies (or a similar mass of bovine hypothalamic tissue) on the secretion of luteinising hormone (LH) from bovine adenohypophyseal tissue (anterior pituitary - AP). When hypothalamic tissue was incubated with AP tissue, an increased amount of LH was released into the medium but no marked increase in LH secretion was observed when pineal bodies were included in the AP culture system. Additionally, the amount of radio-immunologically active luteinising hormone-releasing hormone (LHRH) contained in bovine pineal bodies was much less than that contained in an equivalent mass of hypothalamic tissue. Thus, present results do not support the concept that the pineal body contains comparatively large amounts of lhrh.