Captive Atlantic cod (Gadus morhua) were fed at four ration levels (starvation, maintenance, moderate, and excess) for periods of 6–9 mo prior to and during spawning. At the end of the experiment, water, protein, glycogen, and fat contents of the liver, white muscle, and ovary were estimated. The depletion of the white muscle and liver was related to oocyte maturation and in particular to the proportion of eggs spawned (PES). The influx of protein into the ovary, the mean hydrated egg diameter, and the egg dry weight all reached maximum values at 10% PES and subsequently declined. Mean vitellogenic oocyte diameter was small prior to spawning but rose to a maximum at PES = 10%. Cod with high condition factors produced more previtellogenic oocytes and used a larger fraction during vitellogenesis. Actual fecundity of specimens deprived of food during the spawning period was between 20 and 80% of the potential fecundity depending on the nutritional status of the fish. Intensity of atresia in moderate ration fish increased from 0% at PES = 0% to 33% at PES = 80%. Estimates of durations of α-atretic vitellogenic oocytes varied between 10 and 13 d at 8 °C assuming a spawning period of 50 d.

Data sets on CB concentrations in fish-eating mammals from five laboratories were combined to test and refine a pharmacokinetic model. Clear differences in PCB patterns were observed between species. The ability to metabolize chlorobiphenyl (CB) congeners with vicinal H-atoms only in the ortho- and meta-positions and with one ortho-chlorine substituent generally increased in the order otter < cetaceans (harbor porpoise, common dolphin) < phocid seals (harbor and grey seal), but the metabolism of congeners with vicinal H-atoms in the meta- and para-positions and with two ortho-chlorines increased in the order cetaceans < seals < otter. Both categories of congeners are probably metabolized by different families of cytochrome P450 (1A and 2B) of which levels apparently differed between the cetaceans, the pinnipeds, and the otter. Within-species CB patterns differed in a concentration-dependent manner. The induction of cytochrome P450 enzymes offers the most likely explanation for this phenomenon, but starvation could have a similar effect on occasion.

Exploratory discharge of produced water and drilling cuttings from oil and gas production has become a major source of pollutant to the biota. The aim of this study is to review previous research on the environmental effect of such exploratory wastes with emphasis on the Niger Delta region. Drilling waste is composed of Aliphatic Hydrocarbon, Polynuclear Aromatic Hydrocarbon (PAH) and heavy metals such as cadmium, chromium, lead, mercury, arsenic , copper, Iron, lead, manganese, zinc, barium and strontium among others which are toxic to the environment. The composition and characteristics of naturally occurring chemical substances in produced water (PW) are closely associated to the geological characteristics of each reservoir. The toxicity of produced water effluent can be reduced when treated before discharging into the sea. Sulphide reducing microorganism which are associated with produced water pose threat to the environment. Barite and bentonite present in most drilling fluid were found to reduce plant growth. Studies in some part of the Niger delta have shown high level of some heavy metals associated with exploratory waste with concentrations higher than world health organization (WHO) standard; these have negative impact on the environment such as massive destruction to aquatic lives and agriculture.

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