Marine and Freshwater Research
Volume 66
Number 10 2015
Sound management of sea cucumber fisheries requires biological information including body measurements. We used hierarchical Bayesian errors-in-variables models to establish correlations among three types of weight measures and two body dimensions. The results can be applied to sea cucumbers in other areas and can be useful for data standardisation and size-based fisheries management.
I used targeted visual surveys to study giant Pacific octopuses (Enteroctopus dofleini) an important by-catch species in pot fisheries in Alaska. I found a significant negative correlation of octopus counts with winter sea-surface temperatures over the past 30 months. Environmental variables affecting recruitment together with visual surveys may allow better prediction of trends in octopus abundance than by-catch statistics.
Ocean acidification (OA), caused by increased levels of carbon dioxide (CO2) in the sea water, has previously been reported to affect the behaviour of fishes. Here, we find that some behaviours (lateralisation and freezing) were affected by OA in three-spined sticklebacks, but the general response to a bird predator (spatial avoidance) was not affected. Thus, the general avoidance behaviour appears to be robust to elevated CO2 levels, despite some behaviours being altered.
The environmental factors influencing breeding of a temporary wetland breeding frog (Litoria olongburensis) from eastern Australia were examined. The species showed breeding flexibility in response to highly variable and unpredictable rainfall conditions. This flexibility may reflect an adaptive capacity to predicted changes in frequency and reliability of precipitation as a result of climate change, and may apply to other temporary wetland species.
White sharks aggregating at fur seal colonies near Stewart Island, southern New Zealand, were tagged to identify their temporal and spatial patterns of occupancy, and to inform management measures that aim to separate sharks from fishing effort. White sharks were present from late summer to early winter, peaking in autumn (March–June). The population comprised mainly subadult and adult males and subadult females, and individual sharks showed fine-scale spatial and temporal variability in abundance. These sharks travel well beyond their aggregation sites, but the behaviour and dynamics of white sharks in other parts of New Zealand remain poorly understood.
Floodwater returning from floodplains can contain large amounts of carbon, but it’s not well understood whether or not this carbon is involved in the carbon budgets of rivers. We examined carbon dynamics upstream and downstream of a river red gum forest, before and after a flood inundated the forest and returned to the river. The flood waters led to a major increase in the carbon budget of the river and the carbon was processed by riverine biofilms, showing carbon from the floodplain can fuel river foodwebs.
Growth of stocked and wild Lates calcarifer in some north Queensland habitats was both seasonal and prey-dependent. In the lower, freshwater Johnstone River, where larger prey appeared depauperate, L. calcarifer grew slower relative to those in downstream estuarine and adjacent coastal areas and in nearby Lake Tinaroo. Growth of L. calcarifer was highly seasonal with marked declines during the cooler months.
Southern calamary are an important fisheries species and understanding levels of connectivity across their distribution is important for management purposes. Genetic discrimination techniques suggested that there is a high level of gene flow and connectivity throughout their distribution. Such results indicate the southern calamary population has the potential to maintain a level of resilience to altering conditions if large scale mixing is maintained.
The Coral Triangle, including Indonesia, is a hotspot for coral reef diversity, but the effects of coral disease in this region are poorly understood. This study reports changes in coral cover and disease prevalence in a remote part of Indonesia, and relates these changes to features of the coral community. Declines in coral cover and increases in both the number of diseases and overall disease prevalence over a 7-year period underlie potential changes in coral communities in this biodiversity hotspot.