Environmental effects on behavioural development consequences for fitness of captive-reared fishes in the wild.

Why do captive-reared fishes generally have lower fitness in natural environments than wild conspecifics, even when the hatchery fishes are derived from wild parents from the local population? A thorough understanding of this question is the key to design artificial rearing environments that optimize post-release performance, as well as to recognize the limitations of what can be achieved by modifying hatchery rearing methods. Fishes are generally very plastic in their development and through gene-environment interactions, epigenetic and maternal effects their phenotypes will develop differently depending on their rearing environment. This suggests that there is scope for modifying conventional rearing environments to better prepare fishes for release into the wild. The complexity of the natural environment is impossible to mimic in full-scale rearing facilities. So, in reality, the challenge is to identify key modifications of the artificial rearing environment that are practically and economically feasible and that efficiently promote development towards a more wild-like phenotype. Do such key modifications really exist? Here, attempts to use physical enrichment and density reduction to improve the performance of hatchery fishes are discussed and evaluated. These manipulations show potential to increase the fitness of hatchery fishes released into natural environments, but the success is strongly dependent on adequately adapting methods to species and life stage-specific conditions.

Effects of rearing density and dietary fat content on burst-swim performance and oxygen transport capacity in juvenile Atlantic salmon Salmo salar.

The effects of hatchery rearing density (conventional or one third of conventional density) and feeding regime (high or reduced dietary fat levels) on burst-swim performance and oxygen transport capacity were studied in hatchery-reared Atlantic salmon Salmo salar, using wild fish as a reference group. There was no effect of rearing density or food regime on swimming performance in parr and smolts. The maximum swimming speed of wild parr was significantly higher than that of hatchery-reared conspecifics, while no such difference remained at the smolt stage. In smolts, relative ventricle mass was higher in wild S. salar compared with hatchery-reared fish. Moreover, wild S. salar had lower maximum oxygen consumption following a burst-swim challenge than hatchery fish. There were no effects of hatchery treatment on maximum oxygen consumption or relative ventricle mass. Haemoglobin and haematocrit levels, however, were lower in low-density fish than in fish reared at conventional density. Furthermore, dorsal-fin damage, an indicator of aggression, was similar in low-density reared and wild fish and lower than in S. salar reared at conventional density. Together, these results suggest that reduced rearing density is more important than reduced dietary fat levels in producing an S. salar smolt suitable for supplementary release.

Less is more: density influences the development of behavioural life skills in trout.

Theory suggests that habitat structure and population density profoundly influence the phenotypic development of animals. Here, we predicted that reduced rearing density and increased structural complexity promote food search ability, anti-predator response and the ability to forage on novel prey, all behavioural skills important for surviving in the wild. Brown trout were reared at three densities (conventional hatchery density, a fourth of conventional hatchery density and natural density) in tanks with or without structure. Treatment effects on behaviour were studied on trout fry and parr, whereupon 20 trout from each of the six treatment groups were released in an enclosed natural stream and recaptured after 36 days. Fry reared at natural density were faster to find prey in a maze. Moreover, parr reared at natural density were faster to eat novel prey, and showed more efficient anti-predator behaviour than fish reared at higher densities. Furthermore, parr reared at reduced densities were twice as likely to survive in the stream as trout reared at high density. In contrast, we found no clear treatment effects of structure. These novel results suggest that reduced rearing densities can facilitate the development of behavioural life skills in captive animals, thereby increasing their contribution to natural production.

Growth hormone increases predation exposure of rainbow trout.

The energetic state of an animal strongly influences decisions that balances feeding against predation risk. Growth hormone increases the metabolic demands, which should elevate the feeding motivation of an animal. This, in turn, may increase the willingness to risk exposure to predators during feeding. To test this hypothesis, we studied the effect of growth hormone on the behavioural response of rainbow trout (Oncorhynchus mykiss) to simulated attacks from a model heron. After attacks, growth hormone treated trout foraged closer to the water surface, resumed feeding earlier, and ate more food than did control trout. Such behaviour should increase the susceptibility to aerial predation. Thus, predation may select against high endogenous growth hormone secretion in wild fish. Furthermore, genetic manipulations to increase growth hormone levels, intended to improve growth performance in aquaculture, may result in individuals with substantially altered behavioural patterns. In light of the increasing potential for interactions between farmed and wild fish, growth hormone transgenic fish may pose a threat to wild fish populations.

Coping with divided attention: the advantage of familiarity.

The ability of an animal to perform a task successfully is limited by the amount of attention being simultaneously focused on other activities. One way in which individuals might reduce the cost of divided attention is by preferentially focusing on the most beneficial tasks. In territorial animals where aggression is lower among familiar individuals, the decision to associate preferentially with familiar conspecifics may therefore confer advantages by allowing attention to be switched from aggression to predator vigilance and feeding. Wild juvenile brown trout were used to test the prediction that familiar fishes respond more quickly than unfamiliar fishes to a simulated predator attack. Our results confirm this prediction by demonstrating that familiar trout respond 14% faster than unfamiliar individuals to a predator attack. The results also show that familiar fishes consume a greater number of food items, foraging at more than twice the rate of unfamiliar conspecifics. To the best of our knowledge, these results provide the first evidence that familiarity-biased association confers advantages through the immediate fitness benefits afforded by faster predator-evasion responses and the long-term benefits provided by increased feeding opportunities.

Adriamycin-methotrexate combination chemotherapy of advanced carcinoma of the cervix: a third look.

Twenty-four consecutive women with recurrence and/or metastasizing carcinoma of the cervix were treated with adriamycin and methotrexate. All patients had previously been treated with external irradiation and 2 intracavitary radium applications. The median recurrence-free interval was 22 months. All patients were evaluable. Five patients (21%) had partial remission for a median duration of 5 months (2 to 9 months), and 7 patients had static disease. When used in dosages that do not precipitate dangerous toxicity this therapy is not effective and in the authors' opinion should be abandoned.

Correlation between estradiol-17 beta and progesterone cytosol receptor concentration, histologic differentiation and 3H-thymidine incorporation in endometrial carcinoma.

Women treated with estrogen exhibit a higher risk of developing endometrial cancer. steroid hormones exert their effects on target tissue through specific cytosol receptor protein. Knowledge of this steroid receptor concentration in endometrial carcinoma might facilitate the treatment of recurrences. We have compared the concentrations of endometrial estrogen and progesterone cytosol receptors with the histologic grade of endometrial carcinoma as well as the rate of 3H-thymidine incorporation. We found a significant difference in receptor concentration between well-moderately differentiated tumours and poorly differentiated ones. No correlation was found between 3H-thymidine incorporation rate and differentiation. A positive correlation between thymidine incorporation rate and progesterone receptor concentration was noticed. The concentration of receptors varies within a wide range of each group of differentiation; thus 23% and 4% of the poorly differentiated tumours had higher concentration of estradiol and progesterone receptors respectively than the median values for well differentiated tumours.

Lactate levels in the rabbit cornea and aqueous humor subsequent to non-gas permeable contact lens wear.

The validity of using the aqueous humor lactate concentration as an indicator of corneal lactate production was tested. For this purpose, ten rabbits wore non-gas permeable contact lenses on one eye for 12 hours. Aqueous humor and corneal extracts were assayed for lactate by means of an enzymatic technique. The contact lens wear caused a limited increment in the corneal lactate concentration, but no change was recorded in the aqueous humor. We therefore conclude that the corneal lactate production has a negligible effect on the lactate concentration in aqueous humor. However, significant individual variations in lactate levels were recorded in the present study, as in earlier ones. Insufficient specificity in the currently used techniques for lactic acid concentration determination may in part explain this.

CO2 laser for the treatment of invasive vulvar and vaginal cancer.

In a material of 21 patients including 7 primary and 6 recurrent vulvar carcinomas, 5 vaginal carcinomas, 1 urethral carcinoma and 2 preinvasive vulvar carcinomas operation was performed with a CO2-laser scalpel. In 9 radical and 3 partial vulvectomies no primary closing of the wounds was performed. In the remaining primary closing was performed. The operative bleeding and healing process with laser scalpel and electrosurgical scalpel using open wound technique were about the same. The surgical time was longer with the laser technique but the operative specimens were better preserved. Healing of the primary closed wounds were uncomplicated.

Human malignant melanoma heterotransplanted to nude mice.

Five different human malignant melanoma were heterotransplanted subcutaneously to nude mice. When small tissue pieces were used 3 out of 5 tumors grew. Subcutaneous injections of suspended tumor cells were also made, but all failed to take. Metastatic or infiltrative growth was never seen in the mice observed for up to 2.5 months. The successful grafts largely retained the original morphologicaL features. The three successfully transplanted tumors could all be serially transferred with 100% tumor take. In one case passage time was reduced from 40 days to 15 days. As measured with 3H-thymidine incorporation the proliferation rate increased during the passages. These changes might be due to a selection of more rapidly growing tumor cells in the nudes.

Influence of "nuclear" estrogen receptor content on prognosis of early stage carcinoma of the uterine body. A short-time follow-up.

Sixty-five patients with Stage I and II endometrial carcinoma were investigated. After a short-time follow-up (17-24 months) significant differences in frequency of relapses were observed between patients with tumors containing low amounts of estrogen receptor (ER less than 60 fmol/mg DNA) in the nuclear pellet, and those with tumors containing greater than 60 fmol ER/mg DNA (p = 0.01). Other prognostic factors showed no differences in frequency of relapses. In this small patient material with a short-time follow-up we therefore suggest that ER in the nuclear pellet may be an important prognostic factor.

Effects of simulated acid rain on growth rate in a spruce-living spider.

Growing juveniles of the spruce-living spider Pityohyphantes phrygianus were sprayed with water of different acidity--pH approximately 7 (control), 4.0 (acid rain) and 2.2-in a 2.5-month laboratory experiment. The growth rates did not differ between control and pH 4.0, while there was a significant growth reduction at pH 2.2. A low mortality occurred only in the pH 2.2 group. P. phrygianus seems to be resistant against acid rain although negative long-term effects cannot be ruled out.