Cameron B. Portt

Exposure to bleached kraft pulp mill effluent disrupts the pituitary-gonadal axis of white sucker at multiple sites

Our recent studies have demonstrated reproductive problems in white sucker (Catostomus commersoni) exposed to bleached kraft pulp mill effluent (BKME) at Jackfish Bay on Lake Superior. These fish exhibit delayed sexual maturity, reduced gonadal size, reduced secondary sexual characteristics, and circulating steroid levels depressed relative to those of reference populations. The present studies were designed to evaluate sites in the pituitary-gonadal axis of prespawning white sucker affected by BKME exposure. At the time of entry to the spawning stream, plasma levels of immunoreactive gonadotropin (GtH)-II (LH-type GtH) in male and female white sucker were 30- and 50-fold lower, respectively, than the levels in fish from a reference site. A single intraperitoneal injection of D-Arg6, Pro9N-Et sGnRH (sGnRH-A, 0.1 mg/kg) increased plasma GtH levels in male and female fish at both sites, although the magnitude of the response was greatly reduced in BKME-exposed fish. Fish at the BKME site did not ovulate in response to sGnRH-A, while 10 of 10 fish from the reference site ovulated within 6 hr. Plasma 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P) levels were depressed in BKME-exposed fish and unlike fish at the reference site, failed to increase in response to sGnRH-A. Testosterone levels in both sexes and 11-ketostestosterone levels in males were elevated in fish from the reference site but were not further increased by GnRH treatment. In contrast, BKME-exposed fish exhibit a transitory increase in testosterone levels in response to the GnRH analog. In vitro incubations of ovarian follicles obtained from fish at the BKME site revealed depressed basal secretion of testosterone and 17,20 beta-P and reduced responsiveness to the GtH analog human chorionic gonadotropin and to forskolin, a direct activator of adenylate cyclase. By comparison, ovarian follicles from fish collected at BKME and reference sites produced similar levels of prostaglandin E basally and in response to a phorbol ester and calcium ionophore A23187, suggesting that BKME effects on ovarian function are selective and do not reflect a general impairment of ovarian function. BKME-exposed fish had plasma levels of testosterone glucuronide proportionately lower than those of reference fish, suggesting that there are site differences in the peripheral metabolism of steroids. These studies demonstrate that BKME exposure affects reproduction by acting at multiple sites in the pituitary-gonadal axis.

Changes in hepatic mixed-function oxygenase (MFO) activity, plasma steroid levels and age at maturity of a white sucker (Catostomus commersoni) population exposed to bleached kraft pulp mill effluent

Abstract The impacts of bleached kraft mill effluent (BKME) on a white sucker (Catostomus commersoni) population were examined during May, July and August 1989, and compared with two reference sites. At the time of this study, the effluent received only primary treatment. BKME-exposed white sucker exhibited increased liversomatic indices and elevated mixed-function oxygenase (MFO) activity in both July and August. They also showed lower gonadosomatic indices and an increased age to maturity. The females contained fewer eggs at maturity, while the males had reduced development of secondary sexual characteristics. These fish also had severe reductions in plasma steroid levels throughout the year, including testosterone, and 17α,20β-dihydroxyprogesterone in both sexes, as well as 11-ketotestosterone in males and 17β-estradiol in females. BKME-exposed white sucker were shorter, older and had decreased growth rates compared to those at the reference sites. These fish also exhibited an increased condition factor, yet showed decreased visceral lipid stores. Relative to those at the reference sites, the stomach contents of the BKME-exposed fish revealed reduced numbers of organisms per gut, reduced taxa per gut and an increased number of empty stomachs. The decreased energetic commitment to reproduction, along with the increased condition factor, suggested a disruption in metabolic capability and altered energy allocation in fish exposed to BKME.

Milt characteristics, reproductive performance, and larval survival and development of white sucker exposed to bleached kraft mill effluent

White sucker from a Lake Superior bay which receives bleached kraft mill effluent (BKME) show increased hepatic mixed-function oxygenase (MFO) activity, reduced plasma sex steroid levels, decreased egg and gonad size, a decrease in the occurrence of secondary sexual characteristics, and an increased age to maturation. This study evaluated the reproductive performance of that white sucker population relative to a similar reference population. Spawning male white sucker from the BKME site had reduced spermatozoan motility but no significant differences in milt volume, spermatocrit levels, or seminal plasma constituents. BKME male and female fish had equal or greater fertilization potential compared to both male and female fish at the reference site. There was no difference either in the hatchability of the eggs or in larval size at hatch. BKME larvae did show reduced growth rates by 24 days posthatch but showed equal rates of yolk utilization. No difference in larval MFO activity was detected between sites at 21 days posthatch, indicating no parental transfer of induction to the progeny.

Hepatic Mixed Function Oxidases Induced in Populations of White Sucker, Catostomus Commersoni, from Areas of Lake Superior and the St. Marys River

Abstract Mixed function oxidases (MFO) are a family of inducible enzymes which oxygenate natural and synthetic chemicals alike, making them amenable to conjugation and excretion. The utility of MFO induction in white suckers as an indicator of chemical contamination was examined in three “areas of concern,” Jackfish Bay, St. Marys River, and the Kaministiquia River. MFO determinations in spawning suckers suggested no induction, although white suckers captured in the summer from Jackfish Bay had MFO levels up to 6 (2,5-diphenyloxazole metabolism) and 7 (Benzo-a-pyrene hydroxylase) fold higher than did reference suckers. Similar induction was found in suckers collected in the summer from the Kaministiquia River and from the St. Marys River, hepatic MFO activities 3 (PPO) and 5 (Ba P) times those of the reference populations suggesting exposure to chemicals with MFO inducing potential. The relative induction of hepatic MFO at all three polluted locations is a sensitive measure of industrially discharged xenobiotics, which might be useful in monitoring the efficiency of remedial action plans.

A potential source of error when estimating ecological production of fishes using back-calculations

SynopsisFish production estimates determined from weights back-calculated to the time of annulus formation were found to underestimate actual production by 12 to 44%. It is suggested that production should either be estimated from weights at the time of collection or a correction factor should be employed when back-calculating weights.

Ecologically Sensitive Channel Design for Urban Receivers: Case Studies.

Historically, engineering practice for managing urban runoff in natural watercourses related to the provision of flood and erosion protection, with typically a…