Environmental influences on histological changes in the reproductive cycle of four New South Wales sea urchins

The suitability of a sea urchin population for commercial harvesting and culturing depends on the timing and duration of the spawning season. Pilot studies have shown that the New South Wales echinoids produce mature gonads for several months.Investigations were made into the influence of those exogenous factors which could be modified under aquacultural conditions.Temperature and food appeared to affect gonad (roe) development, while depth and density did not. The relationship between macro and micro changes in the gonads was established and methods of estimating stages of gametogensis were compared.     

INVESTIGATION OF SHEEP DIPS

Groups of 30 sheep of four breeds (Merino, Dorset Horn, Romney Marsh and Border Leicester), that had been maintained under the same environmental and nutritional conditions were used in showering experiments with a diazinon emulsion. The fleeces of all breeds stripped (or depleted) diazinon from the dipping fluid. Diazinon was not deposited evenly down the length of the wool staple. On the Merino fleece, more diazinon was deposited on the outer section and less on the inner section near the skin. On the other breeds, more diazinon was found in the inner and less on the outer sections. Differences in the magnitude and location of the diazinon deposits are discussed, with the aid of supplementary in vitro dipping experiments, in relation to the compactness of the fleece and the amounts and distribution of wax, suint and dirt found there.     

Surveillance for highly pathogenic avian influenza in migratory shorebirds at the terminus of the East Asian-Australasian Flyway

AIM: To determine if migratory birds arriving in New Zealand in the Southern Hemisphere spring of 2004 were infected with the highly pathogenic avian influenza (AI) virus, H5N1.

METHODS: Cloacal and faecal samples were collected from migratory red knots following their arrival in New Zealand in October 2004. Two species of resident sympatric birds, wrybill and mallard duck, were sampled prior to, and following, the arrival of migratory birds.

RESULTS: No AI viruses were isolated from migratory or resident shorebirds. Non-pathogenic AI viruses were isolated from six resident mallard ducks, comprising the endemic subtypes H4 (n=2), H7 (non-pathogenic), H10, and H11 (n=2).

CONCLUSIONS: Highly pathogenic AI H5N1 virus was not detected in migratory shorebirds or sympatric water birds in the Firth of Thames, New Zealand, in 2004-2005, despite the possible proximity of migratory birds to outbreaks of the disease in East Asia in 2004.     

The source of autumn and spring downstream migrating juvenile Atlantic salmon in a small lowland river

Over 3 years, 32,444 age‐0 group Atlantic salmon (Salmo salar) parr tagged with passive integrated transponder tags throughout the River Frome catchment were assigned to one of three groups, nonmigrants, autumn migrants and spring smolts, depending on the detection and the timing of detection at downstream tag readers (situated 8.6 km above the tidal limit). We examined the effect of density at the time of tagging (n·m^?2), distance upstream from the tidal limit (km), fish length (mm), Fulton condition index, habitat type (divided into two types, main river and carrier), days after 1 September that each fish was tagged and year (replication) on the proportions of fish in each of the migration groups. Distance upstream from tidal limit was strongly negatively related to the proportion of autumn migrants and positively related to the proportion of spring smolts. Nonmigrants had a lower average body size than migrants, although there were no differences in the sizes of autumn migrants and spring smolts in September prior to migration. Fish density had no effect on migration strategy. A lower proportion of fish migrated as autumn migrants from the smaller carrier habitats than the main river channel. There is some evidence that those parr destined to become autumn migrants underwent a lower mortality rate during September before tagging than those destined to become spring migrants indicating possible physiological or behavioural differences between these two groups of fish at that time. More research into the factors responsible for initiating the autumn migration is required.     

Predation by invasive signal crayfish on early life stages of European barbel may be limited

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