Cholinesterase response in native birds exposed to fenitrothion during locust control operations in Eastern Australia

Huge aggregations of flightless locust nymphs pose a serious threat to agriculture when they reach plague proportions but provide a very visible and nutritious resource for native birds. Locust outbreaks occur in spring and summer months in semiarid regions of Australia. Fenitrothion, an organophosphate pesticide, is sprayed aerially to control locust plagues. To evaluate fenitrothion exposure in birds attending locust outbreaks, we measured total plasma cholinesterase (ChE), butrylcholinesterase (BChE), and acetylcholinesterase (AChE) activities in four avian species captured pre- and postfenitrothion application and ChE reactivation in birds caught postspray only. Eleven of 21 plasma samples from four species had ChE activity below the diagnostic threshold (two standard deviations below the mean ChE activity of prespray samples). Granivorous zebra finches (Taeniopygia guttata) and insectivorous white-winged trillers (Lalage sueurii) had significantly lower mean plasma total ChE, BChE, and AChE activity postspray, while other insectivores, white-browed (Artamus superciliosus) and masked woodswallows (Artamus personatus), did not. Cholinesterase was reactivated in 19 of the 73 plasma samples and in one of three brain samples. We conclude that native bird species are exposed to fenitrothion during locust control operations. This exposure could have detrimental impacts, as both locust outbreaks and avian reproductive events are stimulated by heavy summer rainfall, leading to co-occurrence of locust control and avian breeding activities.

Short-term food deprivation before a fish oil finishing strategy improves the deposition of n-3 LC-PUFA, but not the washing-out of C18 PUFA in rainbow trout

This study aimed to test the hypothesis that the efficiency of a finishing period can be improved by reducing the initial fat content of fish fillets, by means of a period of food deprivation. Two groups of rainbow trout (Oncorhynchus mykiss) were fed for an 18-week grow-out period on a vegetable oil-based diet (VO) or a fish oil-based diet (FO). VO fed fish were then split into two sub groups: one (VO/FO) was shifted to the FO diet for 8 weeks, whilst the other (UF/FO) was deprived of food (unfed) for 2 weeks and then fed the FO diet for the remaining 6 weeks. The control treatment (FO/FO) was represented by fish continuously fed FO. The subsequent reduction of total fat in the UF/FO treatment was then responsible for a much faster recovery towards a FO-like fatty acid profile, validating the proposed hypothesis. However, the modification of the fatty acid composition of fish fillets during the feed withholding period, coupled with the postponement of the finishing diet, resulted in only minor beneficial effects of this strategy, and the loss of potential weight gain. However, the n-3 LC-PUFA content in UF/VO fish fillets was significantly higher than fish subjected to the VO/FO treatment.

Reproductive development, GnRHa-induced spawning and egg quality of wild meagre (Argyrosomus regius) acclimatised to captivity

The objective of the study was to acclimatise wild-caught meagre (Argyrosomus regius) to captivity to produce viable eggs for aquaculture production. Twelve meagre (3 males and 9 females, mean weight = 20 ± 7 kg) were caught and transported to a land-based facility on 26 October 2006. During, March to June 2007, all three males were spermiating and five of the nine females were in vitellogenesis with mean maximum oocyte diameter ≥550 μm. No spontaneous spawning was observed. Two hormone treatments, either a single injection of gonadotropin-releasing hormone agonist (GnRHa, 20 μg kg−1 for females and 10 μg kg−1 for males) or a slow-release implant loaded with the same GnRHa (50 μg kg−1 for females and 25 μg kg−1 for males), were used to induce spawning on three different dates on 26 March 2007, 4 May 2007 and 18 April 2008. From each spawning event, the following parameters were determined: fecundity, number of floating eggs, egg size, fertilisation and hatching success, unfed larval survival, and proximal composition and fatty acid profile of the eggs. In 2007, two females that were injected on 26 March and 4 May spawned a total of 5 times producing 9,019,300 floating eggs and a relative fecundity of 198,200 eggs kg−1 and two different females that were implanted on the same dates spawned 14 times producing 12,430,000 floating eggs and a relative fecundity of 276,200 eggs kg−1. In 2008, a pair that was implanted spawned five times producing a total of 10,211,900 floating eggs and a relative fecundity of 527,380 eggs kg−1. The latency period was 48–72 h. Parameters were compared between hormone treatments, date of hormone induction and parents determined by microsatellites. Percentage hatch and egg size were 70 ± 0.3% and 0.99 ± 0.02 mm, respectively, for GnRHa-implanted fish and were significantly higher (P < 0.05) compared to 30 ± 0.3% and 0.95 ± 0.03 mm, respectively, for injected fish. Few differences were observed in proximal composition and fatty acid profile and for all spawns mean (% dry weight) lipid content was 17.3 ± 3.0%, carbohydrate was 4.4 ± 1.9% and protein was 31.5 ± 6.4% and the essential fatty acids: Arachidonic acid (ARA, 20:4n-6) ranged between 0.9 and 1% (of total fatty acids), eicosapentaenoic acid (EPA 20:5n-3) 7.7–10.4% and docosahexaenoic acid (DHA 22:6n-3), 28.6–35.4%. All good quality spawns were obtained in the second and/or third spawn after GnRHa treatment, whereas all bad quality spawns were obtained either on the first spawn or after the fifth spawn. Both spawning protocols gave commercially viable (1,000,000+) numbers of good quality eggs that could form the basis of a hatchery production.