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The most common method of estimating teleost ages is via sectioned otoliths. With diminishing funding and policies around cost-recovery from fishing industries, exploring cost-effective methods of estimating ages is warranted. The present study used 18 years of size-at-age data collected from monitoring of the commercial halfbeak (Hyporhamphus australis) fishery off New South Wales, Australia, to predict age classes from otolith weights, while considering other sources of variability such as sex, fish length, and year, month, and location of capture. We observed a significant linear relationship between age class and mean otolith weight. A generalized linear mixed model predicted 1-year olds with an 82% success rate; but was less successful for other ages. Year of sampling explained the greatest variability in the model and the distributions of otolith weights for each age class had considerable overlap. We conclude that substantial inter-annual variability in the age-class to otolith weight relationship, in addition to the relatively low precision when aging H. australis by counting annuli in sectioned otoliths, limits the predictive capacity of this model for future monitoring. Nevertheless, substantial cost savings could be made through recalibrating the model for new samples through direct aging of a subset of otoliths each year. The population of H. australis is continuing to rebuild from a previously overfished state, with an expectation that older fish will become more abundant in the fishery. Age estimation from counting annuli in sectioned otoliths is likely to be the most reliable method of identifying older individuals.

This paper presents a general framework for simulating plot data in multi-environment field trials with one or more traits. The framework is embedded within the R package FieldSimR, whose core function generates plot errors that capture global field trend, local plot variation, and extraneous variation at a user-defined ratio. FieldSimR’s capacity to simulate realistic plot data makes it a flexible and powerful tool for a wide range of improvement processes in plant breeding, such as the optimisation of experimental designs and statistical analyses of multi-environment field trials. FieldSimR provides crucial functionality that is currently missing in other software for simulating plant breeding programmes and is available on CRAN. The paper includes an example simulation of field trials that evaluate 100 maize hybrids for two traits in three environments. To demonstrate FieldSimR’s value as an optimisation tool, the simulated data set is then used to compare several popular spatial models for their ability to accurately predict the hybrids’ genetic values and reliably estimate the variance parameters of interest. FieldSimR has broader applications to simulating data in other agricultural trials, such as glasshouse experiments.

There has been an increasing emphasis on reducing the environmental impacts of penaeid trawls by modifying their anterior sections. In one Australian estuary, this approach has culminated in a new generic trawl comprising a slightly smaller mesh size, and steeper and shorter side panels than traditional trawls, combined with a top panel extending forwards of the bottom panel (termed ‘lead-ahead’) and no headline floats. This study sought to investigate if an additional simple, cumulative modification (tickler chain) might help promote adoption of the new trawl, via improved penaeid catches. Six volunteer fishers towing pairs of either the traditional or new trawls in double rigs were asked if an observer could accompany fishing trips, and alternately attach a light tickler chain (∼3 kg) anterior to the ground gear of one trawl. Regardless of the trawl design, the tickler chains significantly increased the catch weights of penaeids, but relatively more so in the new trawls (by 1.11 × vs 1.08 × ). The tickler chains also significantly increased the number and weight of total bycatch in the traditional trawls (by up to 1.22 × ), but not in the new trawls—although there were variable species-specific effects. In terms of total effects, the data support using tickler chains to increase the efficiency of the new trawls and their cumulative benefits, and could be promoted to facilitate broader inter- and intra-fleet adoption.

In south-eastern Australia, the same baited, round traps (comprising 50–57-mm mesh netting) are used to target giant mud, Scylla serrata and blue swimmer crabs, Portunus armatus in spatially separated fisheries. Both fisheries are characterised by the common, problematic discarding of undersized portunids (