Stress affects reproduction

A short account of how stress interferes with reproduction in farmed fish

Changes in water quality within anglers' keepnets during the confinement of fish

The influence of mesh size and loading density on conditions within keepnets during the confinement of fish was examined. The performance of a mixed-mesh net was also evaluated. Confinement of fish within nets of a standard diameter and length and of three different mesh sizes for 5 hours resulted in no deleterious changes in levels of dissolved oxygen, unionized ammonia, carbon dioxide, or pH at any of three sample points within each net. Transfer of fish to similar nets at a similar, and a higher, loading for 5 hours resulted in a depletion of oxygen, and accumulation of ammonia, in the high-load nets. No changes in carbon dioxide levels or pH were observed in nets containing either moderate or high loads. Confinement of fish in mixed-mesh nets for 5 hours resulted in a depletion of dissolved oxygen in the lower section of the net and an accumulation of unionized ammonia. There were no changes in carbon dioxide, or pH. These results are discussed with reference to the water quality requirements of freshwater fish. It is concluded that changes in water quality within anglers keepnets during the confinement of fish are not of sufficient magnitude to adversely affect the confined fish

Pheromone reception in salmonid fish: identification and characterization of putative steroid receptors in olfactory tissue of brown and rainbow trout

Specific binding sites for testosterone have been detected in three compartments of olfactory tissue from brown and rainbow trout. Binding of 3H-testosterone to the membrane fraction of olfactory tissue is of high affinity (Kd = 0.5 - 1.9 nM) and limited capacity (Nmax= 30 - 60 fmol mg-1 protein). Binding is reversible, and is eliminated by protease treatment. The binding site exhibits a high degree of ligand specificity, 11β-hydroxytestosterone, 11-ketotestosterone, 17α-hydroxyprogesterone, 17α, 20β-dihydroxy-4-pregnen-3-one, cortisol, and estradiol-17β all fail to displace testosterone at 20-fold excess. These attributes are characteristic of specific steroid receptor proteins. Binding of testosterone within the cytosol fraction is of moderate affinity (Kd = 9.0 - 23.0 nM) and high capacity (Nmax = 0.5 - 2.9 pmol mg-1 protein) and binding of testosterone is more readily displaced by a number of steroid competitors than is the case for the membrane site. The rate of association and dissociation of testosterone from the cytosolic binding site is markedly more rapid than the equivalent processes in the membrane fraction. Binding of testosterone to the nuclear extract is of high affinity (Kd ~ 3.0 nM) and limited capacity (Nmax ~ 50 fmol mg-1 protein). There are no marked differences between species or between sexes in the affinity or capacity of testosterone-binding sites in nuclear extract or membrane fraction. However, cytosolic testosterone-binding sites are three- to four-fold more abundant in rainbow trout than in brown trout, and female rainbow trout have more cytosolic binding sites than male rainbow trout, but a lower affinity for testosterone than male sites. Preliminary evidence supports the involvement of the membrane-associated testosterone-binding site in olfactory processes. Rainbow trout display an EOG response to testosterone at a concentration (10-9 M) which is consistent with the equilibrium dissociation constant (Kd) of the membrane-associated testosterone-binding site. The concentration of ligand at which half the binding sites are saturated (Kd) is in the range 0.5 - 2.0 . 10-9 M for membrane-associated testosterone binding. Binding of 3H-testosterone to the membrane-associated site shows a pH dependency which is comparable to the effects of pH on the EOG response to testosterone in intact fish. The data concerning the attributes of the membrane associated testosterone-binding site are consistent with the olfactory tissue of salmonids possessing the capability to respond to testosterone present in the aquatic environment. The intracellular testosterone-binding sites show characteristics common to testosterone receptors in other fish tissues which are known androgen target tissues. This suggests that the development and/or function of salmonid olfactory tissue may be open to influence by endogenous testosterone. This is the first report of androgen binding to olfactory tissue in fish, and the first report of a membrane-associated androgen binding site in fish

Changes in blood cortisol, glucose and lactate in carp retained in anglers' keepnets

Capture of carp from holding tanks by dip-net, or from semi-natural conditions by rod and line, elicits a physiological stress response characterised by elevation of plasma cortisol levels. The transfer of carp to keepnets subsequent to capture does not increase or reduce the magnitude or duration of this response and in both cases plasma cortisol levels have returned to pre-stress levels within 24 hours of the initial disturbance. The post-capture plasma cortisol elevation is accompanied by disturbances in plasma glucose and lactate levels but these are less consistent in severity and duration than the cortisol response. These data suggest that the retention of fish in keepnets following capture, does not represent a source of stress additional to that imposed by capture and has no effect on the rate of recovery of the fish from the initial capture stress

Rapid bioconcentration of steroids in the plasma of three-spined stickleback Gasterosteus aculeatus exposed to waterborne testosterone and 17β-oestradiol

The relationship over time between the concentrations of two steroids, singly and in combination, in a static exposure system and in the blood of three-spined stickleback Gasterosteus aculeatus, held within the exposure system was investigated. Groups of three-spined stickleback were exposed (nominally) to either 1000 ng l1 17β-oestradiol (E2), testosterone (T) or E2 and T in combination at the same concentrations for 6 days. Both water and fish were sampled at intervals and steroid concentrations in both compartments were determined. The plasma steroid time profile revealed a rapid bioconcentration within the first 6 h of exposure. The plasma steroid levels attained at this time point (20–90 ng ml1) were up to 50-fold (E2) and 200-fold (T) greater than the actual levels of steroid measured in the exposure water, while levels in the blood of control fish did not exceed 4 ng ml1. The substantial elevation of plasma steroid levels relative to the concentrations of steroid to which the fish were exposed in the ambient water gives scope for delivery of the steroids to target endocrine tissues at levels far in excess of what might be predicted on the basis of passive branchial uptake alone. These results are discussed in relation to endocrine disruption, and in particular the occurrence of effects in fish exposed to levels of endocrine active substances that are seemingly physiologically irrelevant

Comments on the ecology of grass grub and porina caterpillar

The object of this paper is to discuss the ecology of grass grub, Costelytra zealandica White, and porina, Wiseana cervinata (Walker), New Zealand’s most important pastoral insect pests, and to survey what has been achieved in ecological understanding of these insects. The biology and ecology of either or both insects have previously been reviewed by Dumbleton (1942), Miller (1945), Kelsey (1951a, b) and Hoy (1963). The lack of fundamental biological information on grass grub (and this is equally applicable to porina caterpillar) and the need for longterm team studies were stressed, although little sustained, co-ordinated research has since eventuated. Examination of the literature clearly indicates that the lack of fundamental ecological research on these pasture pests is directly due to the introduction of organochlorine insecticides, particularly DDT, to control both porina and grass grub. These insecticides proved cheap, persistent in soil, relatively safe to handle and easy to apply (Kelsey and Hay., 1950; Kelsey 1951a, b, 1952, 1959). DDT was so effective that it led to complacency, in spite of the warning by Miller (1945) that in his view no single control would suffice. There was failure to anticipate: (1) Development of insect resistance. to insecticides. (2) Possible alteration of tolerance limits for insecticides in foodstuffs, by countries importing New Zealand produce. (3) Failure of DDT to be effective in certain soils. (4) The need for fundamental knowledge, in case the efficacy of DDT and related insecticides diminished, and new methods had to be found

Digital preservation the hard way

Poster presented at the Open Repositories 2015 conference on June 9, 2015.An awesome tool set for digital preservation is available to all institutions who use DSpace. This is not a story of how we used this tool set. This is a story of how we recovered from an accidental deletion of a significant number of items, collections, and communities--an entire campus's ETDs: 315 missing items, 878 missing bitstreams, 1.4GB of data, 7 missing communities, 11 missing collections--using a database snapshot and a tape backup. The SQL we developed to facilitate this restoration may be helpful, but it is our hope that in comparison, the effort required to implement a proper backup and preservation safeguard, such as DuraCloud and/or the Replication Task Suite, will rightly seem more appealing. In other words: here's how to do it the wrong way, but you'd really be better off doing things the right way. This poster should be sufficient to serve as a guide for actually recovering from an accidental deletion of materials in DSpace, if one only has a database snapshot and a tape backup of a DSpace assetstore. It will also serve as a reminder of the digital preservation tool set available for DSpace, as well as why these tools exist.Includes bibliographical references

The effects of environmental stress on the physiology of growth in rainbow trout, Salmo gairderi Richardson

There is little doubt that both mammalian and teleost growth hormones can accelerate growth and increase food conversion efficiency in all commonly-reared species of salmonid fish. In those vertebrates that have been closely studied (predominantly mammals), the pituitary hormone somatotropin (GH or growth hormone) is a prime determinant of somatic growth. The hormone stimulates protein biosynthesis and tissue growth, enhances lipid utilization and lipid release from the adipose tissues (a protein-sparing effect) and suppresses the peripheral utilization of glucose. The present study is a prerequisite for future work on growth hormone physiology in salmonids and should contribute to our understanding of the mechanisms of growth suppression in stressed fish. Plasma growth hormone (GH) levels were measured in rainbow trout using a radioimmunoassay developed against chinook salmon growth hormone

Indicators of reproductive performance in rainbow trout Oncorhynchus mykiss (Walbaum) selected for high and low responsiveness to stress

A number of indicators of reproductive performance were assessed in rainbow trout divergently selected on the basis of their plasma cortisol response to a standardised stressor. For both male and female rainbow trout, body weight was significantly related to stress responsiveness. High-responding (HR) females were significantly heavier than low-responding (LR) females overall and HR males were significantly heavier than LR males overall. There was no significant difference in the SGR of HR and LR female fish during the experimental period while in contrast the mean SGR of HR males was significantly greater than that of LR males. The divergent confinement-induced levels of blood cortisol in HR and LR groups were stable for more than one year after selection. There was no significant difference in the extent to which confinement stress reduced blood estradiol-17 levels in HR and LR females despite the large difference in relative blood cortisol levels. The onset and rate of ovulation was similar within the HR and LR groups. Differences in fecundity, relative fecundity and egg volume and weight were wholly attributable to the different mean body weights of the HR and LR fish. There was no difference between the sperm counts of HR and LR males. There was significantly higher mortality among eggs derived from HR parents overall between fertilization and hatch but maximum mean mortality did not exceed 12%. Mean time to eyeing in the HR groups was 224 degree days and in the LR groups was 244 degree days. Hatching commenced at 344 and 347 degree days in the HR and LR groups respectively and was complete within 412 and 416 degree days respectively. Overall, selection for stress responsiveness was associated with no significant benefits or costs in reproductive performance