This study aimed to determine the effect of post harvest operations such as
air exposure on the health status of lobsters. These effects can be assessed
through measurement of selected immune parameters such as total haemocyte
counts, haemolymph clotting time, bacteraemia and the differential proportion
of granular cells in lobster haemolymph. Lobsters were taken from factory
holding tanks and exposed to air for 2, 6, 12, and 18 h through placement in
foam boxes. Controls were sampled at each time point by collecting lobsters
from the same tank as the experimental animals (10 animals /treatment
group) with a different group of lobsters being sampled at each time point.
Air exposure caused a significant increase in clotting time at 12h and 18h.
Total haemocyte counts showed a decreasing trend. The proportion of granular
cells tended to be lower in air-exposed animals, the difference was
significant at 2h exposure. The bacteraemia levels tended to be higher in air
exposed lobsters than in controls and the difference was significant at 12h
exposure. Low total haemocyte counts, high clotting times, low granular cell
numbers and high bacteraemia levels implied increased susceptibility to
infection and lowered immunity. The results show that air exposure has a
significant adverse effect on the immune system and hence on the health status
of the lobsters.
Shark depredation is an issue of concern in some Western Australian recreational and commercial fisheries where it can have economic, social and ecological consequences. Knowledge of the shark species involved is fundamental to developing effective management strategies to mitigate the impacts of depredation. Identification of the species responsible is difficult as direct observation of depredation events is uncommon and evaluating bite marks on fish has a high degree of uncertainty. The use of trace DNA techniques has provided an alternative method for species identification. We demonstrate proof of concept for a targeted DNA barcoding approach to identify shark species using trace DNA found at bite marks on recovered remains of hooked fish. Following laboratory validation, forensic analysis of swabs collected from samples of bitten demersal fish, led to the definitive identification of shark species involved in 100% of the incidences of depredation (n = 16).
In the present study, we investigate the potential impact of the first proposed interstate translocation of mussel spat, for aquaculture enhancement, on the genetic integrity of Mytilus populations in Western Australia (WA). We performed genetic analysis on four populations (Garden Island, Bunbury, Albany and Esperance) in WA and on mussels from three hatcheries in South Australia (SA), Victoria (Vic) and Tasmania (Tas) proposed as spat sources in the translocation application. Two genetically distinct groups of M. galloprovincialis were identified, which corresponded to introduced Northern Hemisphere and native Southern Hemisphere haplotypes. Mussels obtained from the hatcheries showed a marked proportion of native haplotypes, while mussels of three (Garden Island, Bunbury and Esperance) of the four sampled WA Mytilus populations consisted mostly of introduced haplotypes. Most importantly, all samples were notable for a mixture of native and introduced haplotypes with the great majority of introduced haplotypes occurring in both WA and eastern states samples. Based on these results, it seems unlikely that the proposed translocation of mussel spat could negatively impact WA Mytilus populations. The current study presents valuable information regarding the genetic composition of Mytilus populations and will prove useful in the assessment of future translocation applications and biodiversity of mussel species in WA.
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