Breeding fish reproduction

Water birds have not been shown to be directly affected by acidification. However, the prey of waterbirds may be of concern as these lower food-chain organisms may have elevated levels of toxic metals related to acidification of their habitat. Moreover, most water birds rely on some component of the aquatic food-chain for their high protein diet. Invertebrates that normally supply caJcium to egg-laying birds or their growing chicks are among the first to disappear as lakes acidify. As these food sources are reduced or eliminated due to acidification, bird habitat is reduced and reproductive rate of the birds is affected. The Common Loon is able to raise fewer chicks, or none at all, on acidic lakes where fish populations are reduced 37 and 5S). However, in some isolated cases, food supplies can be increased when competitive species are eliminated (e.g.. Common Goldeneye ducks can better exploit insects as food when competition from fish is eliminated). The collective influences of acidification are difficult to quantify on a specific area basis but for species that rely on a healthy aquatic ecosystem to breed, acidification remains a continuing threat in thousands of lakes across eastern North America 14). 

Seasonal variations in phase I and II enzymes are often seen in conjunction with breeding cycles. This is particularly true in amphibians, fish, and birds and probably reflect underlying endocrine changes associated with the establishment of reproductive competence. For example, in the razorbill, elevated metabolism of organochlo-rine insecticides such as aldrin has been reported in females collected in April-May. This correlated with increased ovarian size and may be related to increases in cir-... 

Contaminated Fish. There were no effects on breeding performance in male minks in the 2-generation reproduction study of Lake Huron fish summarized in Section 3.2.5.3.1 (Restum et al. 1998). No differences in the number of attempted or confirmed matings, or testicular volumes, were observed among the PI and FI generation males. 

Not all characteristics are subject to successful selection pressure. There must be natural variation, differences in reproduction, and inheritability of the trait in order for selection to produce results. Natural selection requires not only that there be genetic variation but also that the genes be expressed (Mulcahy and Mulcahy, 1987). Without the latter, the genetic code present in a BU is simply irrelevant. Those traits that are not genetically determined cannot be selected for. Predation can select for different traits than would otherwise be chosen. An example of this is the color of male guppy fish females breed preferentially with the most colorful ones, but predators can most easily locate and eat the most colorful ones. Thus, male guppies in upland streams where there are few predators are more colorful than guppies downstream where predators abound (Palumbi, 2001). 

We have been interested in the effect of poly(ADP-ribosyl)ation on chemical carcinogenesis in vivo. The system used was the induction of hepatocarcinogenesis by methylazoxymethanol acetate (MAM acetate) in the small fish Medaka", Oryzias latipes. Medaka was selected as a suitable model animal for the following reasons It is easy to breed, adapts to a wide range of temperatures, is easy to sexually differentiate, has a short reproductive cycle, and is available as a pure strain. In addition, continuous administration to Medaka of the drug is possible by simply dissolving it in tank water. 

Spermatozoa Requires mature broodstock /reproduction control +++ in fish, mollusc +/- in cmstacean Fertilization Cross breeding, requires females from close strains... 

Measures of ecosystem and receptor characteristics Water temperature, water velocity, and physical obstructions abnndance and distribution of suitable pebble substrate for breeding in streams abnndance and distribution of suitable food sources for fry feeding, resting, and breeding behavior of adult fish and natural reproduction, growth, and mortality rates... 

---