Paul L. Jones

Probabilistic risk assessment of agrochemicals in the environment

Concern for the environment has resulted in greater scrutiny of both old and new plant protection products and increased e!orts have been directed to developing more rigorous but more realistic procedures for the ecotoxicological risk characterization of these agrochemicals. These techniques include probabilistic analysis of toxicity and exposure data and better understanding of the relationship between structure and function in populations of wildlife and the role of keystone species in maintaining ecosystem functioning. The ecological risk assessment method described here is centered on the use of probabilistic distribution functions that independently describe exposure concentrations and toxicological responses of organisms to the chemical of concern. The distributions are transformed to permit calculation of linear regression parameters. The regression parameters for the two distributions are then used to determine joint probabilities which interrelate the exposure and toxicology data. For ease of presentation the results are presented as an exceedence plot which depicts, based on the exposure data the percent of species likely to be a!ected and the percent of observations likely to cause this level of e!ect. In this paper, the use of the method is illustrated using data for chlorpyrifos in North American aquatic environments. These probabilistic risk assessment methods are being assessed for incorporation into assessment procedures in a number of regulatory jurisdictions. ( 2000 Elsevier Science Ltd. All rights reserved.

LC-PUFA biosynthesis in rainbow trout is substrate limited: use of the whole body fatty acid balance method and different 18:3n-3/18:2n-6 ratios.

Five experimental diets with constant total C18 PUFA and varying 18:3n-3/18:2n-6 ratios were fed to rainbow trout over an entire production cycle. The whole-body fatty acid balance method demonstrated a clear trend of progressively reduced fatty acid bioconversion activity along the n-3 and n-6 pathways, up to the production of 20:5n-3 and 20:4n-6, respectively. This suggests that the pathway exhibits a “funnel like” progression of activity rather than the existence of a single rate limiting step. The production of 22:5n-3 and 22:6n-3 was more active than that of 20:5n-3. However, despite this trend in reduced apparent in vivo net enzyme activity, the efficiency of the various bioconversion steps (measured as % of bioconverted substrate) confirmed an opposing trend. A 3.2-fold higher Δ-6 desaturase affinity towards 18:3n-3 over 18:2n-6 and an 8-fold greater Δ-5 desaturase affinity towards 20:4n-3 over 20:3n-6 were recorded. The main results of the study were that (1) rainbow trout are quite efficient at bioconverting 18:3n-3 to 22:6n-3, and (2) the LC-PUFA biosynthetic pathway is substrate limited. Fillet n-3 LC-PUFA concentrations increased with the increasing dietary supply of 18:3n-3. Despite an almost identical dietary supply of n-3 LC-PUFA, originating from the fish meal fraction of the diets, the fillets of trout fed the diet richest in 18:3n-3 were 2-fold higher in n-3 LC-PUFA than fish fed low 18:3n-3 diets. Nevertheless, fillets of trout fed a fish oil control diet contained more than double the amount of n-3 LC-PUFA compared to fish fed the diets richest in 18:3n-3.

Traceability and discrimination among differently farmed fish: a case study on Australian Murray cod.

The development of traceability methods to distinguish between farmed and wild-caught fish and seafood is becoming increasingly important. However, very little is known about how to distinguish fish originating from different farms. The present study addresses this issue by attempting to discriminate among intensively farmed freshwater Murray cod originating from different farms (indoor recirculating, outdoor floating cage, and flow through systems) in different geographical areas, using a combination of morphological, chemical, and isotopic analyses. The results show that stable isotopes are the most informative variables. In particular, delta(13)C and/or delta(15)N clearly linked fish to a specific commercial diet, while delta(18)O linked fish to a specific water source. Thus, the combination of these isotopes can distinguish among fish originating from different farms. On the contrary, fatty acid and tissue proximate compositions and morphological parameters, which are useful in distinguishing between farmed and wild fish, are less informative in discriminating among fish originating from different farms.

EFFECTS OF STARVATION AND SUBSEQUENT REFEEDING ON THE SIZE AND NUTRIENT CONTENT OF THE HEPATOPANCREAS OF CHERAX DESTRUCTOR (DECAPODA: PARASTACIDAE)

Abstract The effect of 16 weeks starvation and 6 weeks refeeding on the size and chemical composition of the hepatopancreas of 2 size classes of C. destructor (20–40 g and 40–60 g) maintained at 2 temperatures (10°C and 25°C) was investigated under laboratory conditions. The response to starvation was not influenced by size class. In fed animals, the wet hepatosomatic index (HSIw-%) and dry hepatosomatic index (HSId-mg/g) increased to 7% at week 2 and 36 mg/g at week 10 respectively, whereas in starved animals HSIw and HSId decreased to 2.6% and 3.6 mg/g at week 10 respectively. Hepatopancreas moisture (HM-%) of fed animals decreased to 51% after 10 weeks, whereas in starved animals it increased to a maximum of 81% after 2 weeks. In fed animals, hepatopancreas lipid (HL-mg/g), protein (HP-mg/g), and ash (HA-mg/g) reached a maximum of 30 mg/g at week 10, 7.8 mg/g at week 6, and 2 mg/g at week 4 respectively. Hepatopancreas carbohydrate (HNFE-mg/g) in fed animals fluctuated considerably. In starved animals, HL did not significantly change for the first 4 weeks, and a minimum of 0.5 mg/g occurred at week 8. In contrast, HP decreased for the first 2 weeks to 3 mg/g, and HNFE decreased for 4 weeks to 0.67 mg/g after which no significant change occurred. Ash levels in starved animals generally decreased for 12 weeks to 0.36 mg/g. Low temperature reduced the rate of utilization of hepatopancreas nutrients. About 7 months of starvation at 10°C is required for the hepatopancreas to become nutritionally depleted. Refeeding starved animals resulted in an increase in wet and dry hepatosomatic indices and all hepatopancreas nutrients and a decrease in hepatopancreas moisture. Complete recovery of the hepatopancreas of starved animals following refeeding, to levels recorded in the fed control animals, was recorded for the HSIw, HA, and HNFE. The various hepatopancreas condition indices used here are discussed in relation to their practical value and accuracy in predicting animal condition, and a classification is presented. The adaptive significance of hepatopancreas size and nutrient storage capacity is also discussed.

Response of the yabby, Cherax destructor clark, to natural and artificial diets: phenotypic variation in juvenile growth

Abstract A comparison of juvenile growth performance amongst families of the freshwater crayfish, C. destructor was carried out under laboratory conditions. Three diets, consisting of two pellet diets (15% and 30% protein) and zooplankton, were fed to the juvenile crayfish which were obtained from three families selected randomly from a genetically heterogeneous stock. Juvenile crayfish were stocked at 1 1−1 in 12 ± tanks and did not differ in weight amongst broods at the commencement of a 35 day trial. Growth and survival were found to differ with respect to diet, with zooplankton giving higher growth and greater survival. Growth, but not survival, differed by phenotype with the degree of difference in growth amongst families being dependent, at least in part, upon diet. Diet was also found to have a pronounced effect on the degree of variability in crayfish size within tanks with zooplankton fed animals showing substantially lower levels of variability compared with pellet fed animals of equivalent size.

Influence of differential movement of the marker chromic oxide and nutrients on digestibility estimations in the Australian freshwater crayfish Cherax destructor

Abstract Faeces were obtained from the Australian freshwater crayfish C. destructor (commonly called the yabby) using a faecal collection system. Daily samples were obtained using 2 different protocols: an 8 h feed immediately followed by a single 4 h collection period, and a 2 h feed followed by 2 separate faecal collections at 10 and 14 h thereafter. Faecal samples using the latter protocol were either analysed separately (as early and late collections) or pooled prior to analysis. The composition of the faeces varied according to the time of deposition. The faecal chromium, protein and ash content were 788, 133 and 244% higher, respectively, in early deposited material compared to faeces collected 4 h later. In contrast the late faecal sample contained about 46% more fibre. The faecal collection period (early versus late) and the collection protocol (single versus pooled) strongly influenced the digestibility estimations. Dry matter (DMD) and protein (PD) digestibility coefficients were 14.1 and 61.1% higher, respectively, for the early deposited faeces compared to the late samples. Ash (AD) and crude fibre (CFD) digestibility coefficients were negative for the late deposited faeces and highly positive for the early samples. The chromium and nutrient content of pooled (early + late) samples, and the resultant digestibility coefficients, were arithmetically located between those values for the early and late collections. The single collection protocol resulted in significantly lower dry matter, protein, ash and crude fibre digestibility coefficients (10.1. 2.8, 13.1, and 54.1%, respectively), than for the pooled collection protocol. C. destructor may be capable of selectively processing certain dietary components whereby low nutrient value foods are rapidly transported through the gut. Despite the limitations of using Cr 2 O 3 it is proposed that the errors associated with its use are small providing the majority of the deposited faecal matter is collected.

Effects of replacement of animal protein by soybean meal on growth and carcass composition in juvenile Australian freshwater crayfish

A feed trial was conducted for 59 days with juvenile Cherax destructor, mean weight (se) 0.61 (0.01) g, reared communally and maintained on 16 isoenergetic diets containing crude protein levels of 15, 20, 25, and 30%. For each protein level the fish meal component was replaced by soybean meal to produce diets in which 0, 20, 40, or 60% of the protein originated from soybean meal. Mean percentage weight gain per day ranged from 2.98% (15% protein, 60% soybean meal diet), to 11.75% (30% protein, 40% soybean meal diet). When soybean meal was included at a level of 40–60%, growth rate was reduced relative to that achieved with control diets at 15% and 20% protein levels. In no case did a 20% substitution significantly affect growth over that achieved with controls. A two-way interaction occurred between dietary protein and the level of dietary soybean meal. Feeds of higher protein content appeared to permit higher soybean meal inclusion levels without significantly affecting growth. Increases of 5% protein produced a significant improvement in growth when soybean meal contributed from 40–60% of the total protein. This effect was less pronounced in the control diets and the 20% soybean meal series. The percentages of protein increased and lipid decreased in the carcass as the level of dietary protein increased. A similar effect occurred by increasing the soybean meal substitution level to 60%. An obvious trend in carcass moisture, energy, and ash did not occur. A protein requirement of 30% is apparent when fish meal and soybean meal are included in diets at levels of 20% and 24% respectively. A maximum weight of 14.13 g was recorded for an individual fed the 30% protein, 20% soybean meal diet.

The effect of dietary protein source on growth and carcass composition in juvenile Australian freshwater crayfish

A feed trial was conducted for 12 weeks on juvenile Australian freshwater crayfish (Cherax destructor) (mean weight (SE) 0.82 (0.02)g) maintained on five isoenergetic diets with a protein content of 30%. Diets differed in the primary source of protein used, with meat, snail, soybean, yabby, and zooplankton meals comprising the major protein ingredient, varying from 56–60% of total protein. Mean percentage weight gain per day ranged from 7.57% (yabby meal diet), to 9.42% (snail meal diet). No significant difference occurred in mean weight, percentage weight gain, specific growth rate (%), or survival among diets. A maximum size of 16.44g was attained on the yabby meal diet. Largest mean weight was 8.27g on the snail-based diet. Food conversion ratios were all good, with a minimum value of 0.95 recorded for the snail-based diet. Initial food consumption per day was approximately 5% of mean animal weight, decreasing to around 2.4%, and is collectively described by a power curve. Protein retention ranged from 29.57% in the zooplankton meal diet to 41.15% in the snail-based diet. Carcass composition was influenced by feed type, with the most marked difference occurring in carapace colour. Animals fed the zooplankton-based pellets developed the strongest pigmentation. Recommendations are made for including certain protein-based ingredients in manufactured yabby diets.

Reproductive biology of the eastern shovelnose stingaree Trygonoptera imitata from south-eastern Australia

In applying a quantitative approach to the reproduction of Trygonoptera imitata, the present study contributes to understanding the wide diversity in the reproductive biology of the family Urolophidae and provides insights to help determine phylogenetic relationships. This localised species is taken as bycatch in several inshore fisheries and potentially impacted by a range of other anthropogenic pressures, including introduced species, particularly in shallow-water pupping areas. T. imitata can be characterised as a species of comparatively low matrotrophic histotrophy with an extended period of relatively large eggs in utero (5–8 months) followed by rapid growth of the embryos (4–6 months). The reproductive cycle is annual with parturition occurring during late-February–April, followed immediately by ovulation. Mean size-at-birth is ~225 mm total length and there is a ~1000% gain in mean wet mass from egg (15 g) to full-term embryo in utero (150 g), the lowest reported for any viviparous batoid. Litter size increases with maternal length, reaching a maximum of seven, and sex ratio of embryos is 1 : 1. Maximum length and estimates of the maturity–ogive parameters l50 and l95 are similar for females and males.

Biennial reproductive cycle in an extensive matrotrophic viviparous batoid: the sandyback stingaree Urolophus bucculentus from south-eastern Australia.

Urolophus bucculentus, the largest urolophid species found in southern Australia, exhibits a biennial reproductive cycle. Ovulation occurs during October to January followed by a 15-19 month period of gestation followed by parturition during April to May and a short rest period while the ovarian follicles continue to develop for subsequent ovulation. Male breeding condition peaks during April to June to coincide with the period of parturition. Urolophus bucculentus has the highest matrotrophic contribution reported for any urolophid species, with a mean wet mass gain from egg in utero (4 g) to full-term embryo in utero (250 g) of c. 6250% (maximum c. 7200%), and perhaps explains the biennial female reproductive cycle where 50% of females contribute to each years recruitment. Litter size (one to five) increases with total length (L(T) ). Females reach a longer maximum L(T) (L(Tmax) ) than do males (885 v. 660 mm). The L(T) at maturity for males and females at 50% mature (L(T50) ) is c. 414 mm (63% of L(Tmax) ) for males and c. 502 mm (57% of L(Tmax) ) for females, length at maternity indicates that recruitment production occurs later in life at c. 632 mm L(T) (71% of L(Tmax) ).