Abiotic Factors Influence Surface Water Herbicide Concentrations Following Silvicultural Aerial Application in Oregon's North Coast Range.

Nontarget impacts of routine aerial silvicultural practices on surface water quality are not well documented. Thus, uncertainty remains regarding herbicide treatment effects on ecological and human health. To investigate factors that influence silvicultural herbicide concentrations in surface water and identify any potential risks, we conducted a 2-year study that monitored multiple streams for herbicide residues following aerial application of glyphosate, clopyralid, sulfometuron methyl (SMM), and metsulfuron methyl (MSM). The monitored streams drain recently harvested forest lands that also serve as municipal water sources for nearby communities in western Oregon's north coast range. A paired watershed design targeted predicted episodic pulses with water samples collected before, during, and after herbicide application, and during the first posttreatment storm events. We report no relic herbicide detections in control or test streams. Aerial application of glyphosate, clopyralid, SMM, and MSM resulted in no detections in control streams and only trace, episodic concentrations in test streams. Across all test streams from both study years, maximum SMM and MSM detections (≤0.030 µg/L) consistently occurred during the first storm event at sampling locations closest to the treated harvest unit. Results indicate that proximity to the treatment site, time from application, and rainfall influence herbicide presence and concentrations in surface water. Furthermore, detections of trace SMM and MSM concentrations were more than 25 000-fold and 60 000-fold below federal human health safety benchmarks for chronic exposure, respectively. We provide empirical context for understanding surface water herbicide presence following aerial silviculture application under modern forestry best management practices and identify potential risk to ecological and human health. Integr Environ Assess Manag 2019;00:1-14. © 2019 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals, Inc. on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Plasma nesfatin-1 is not affected by long-term food restriction and does not predict rematuration among iteroparous female rainbow trout (Oncorhynchus mykiss).

The metabolic peptide hormone nesfatin-1 has been linked to the reproductive axis in fishes. The purpose of this study was to determine how energy availability after spawning affects plasma levels of nesfatin-1, the metabolic peptide hormone ghrelin, and sex steroid hormones in rematuring female rainbow trout (Oncorhynchus mykiss). To limit reproductive maturation, a group of female trout was food-restricted after spawning and compared with a control group that was fed a standard broodstock ration. The experiment was conducted twice, once using two-year-old trout (second-time spawners) and once using three-year-old trout (third-time spawners). During monthly sampling, blood was collected from all fish, and a subset of fish from each treatment was sacrificed for pituitaries. Pituitary follicle-stimulating hormone-beta (fsh-ß) mRNA expression was analyzed with q-RT-PCR; plasma hormone levels were quantified by radioimmunoassay (17ß-estradiol and ghrelin) and enzyme-linked immunosorbent assay (11-keto-testosterone and nesfatin-1). Although plasma nesfatin-1 levels increased significantly in the months immediately after spawning within both feeding treatments, plasma nesfatin-1 did not differ significantly between the two treatments at any point. Similarly, plasma ghrelin levels did not differ significantly between the two treatments at any point. Food restriction arrested ovarian development by 15-20 weeks after spawning, shown by significantly lower plasma E2 levels among restricted-ration fish. Pituitary fsh-ß mRNA levels were higher among control-ration fish than restricted-ration fish starting at 20 weeks, but did not differ significantly between treatment groups until 30 weeks after spawning. Within both treatment groups, plasma 11-KT was elevated immediately after spawning and rapidly decreased to and persisted at low levels; starting between 20 and 25 weeks after spawning, plasma 11-KT was higher among control-ration fish than restricted-ration fish. The results from these experiments do not provide support for plasma nesfatin-1 as a signal for the initiation of reproductive development in rematuring female rainbow trout.

Metabolic endocrine factors involved in spawning recovery and rematuration of iteroparous female rainbow trout (Oncorhynchus mykiss).

To determine how energy balance affects metabolic hormones hypothesized to play a role in the onset of a new reproductive cycle in iteroparous salmonids, food availability after spawning was restricted in female rainbow trout. These fish were compared with a control group that was fed a standard brood stock ration. Bodyweight, length, and muscle lipid content were determined, and blood was collected from fish at regular intervals; a subset of fish from each group was sacrificed at each sampling time for the collection of liver and ovary tissue, and to calculate hepatosomatic index (HSI) and gonadosomatic index (GSI). Plasma hormone levels were quantified by radioimmunoassay, and tissue gene expression levels were analyzed using q-RT-PCR. The experiment was conducted twice, using two-year-old and three-year-old post-spawned fish. Food-restriction arrested ovarian growth and development within 15-20 weeks, as evidenced by lower GSI in restricted-ration fish. Food restriction also reduced Fulton's condition factor, muscle lipid content, and specific growth rate from one month onward, and reduced HSI after 3 months. In the liver, insulin-like growth factor (igf1 and igf2) gene expression was reduced in three-year-old food-restricted fish within 2 months; however, no effect of ration on igf1 or igf2 expression was detected in two-year-old fish. In both years, IGF binding protein-1 (igfbp1) gene expression decreased over time in both treatment groups. Liver leptin (slepA1) gene expression was lower in two-year-old food-restricted fish at 4 months. These results show that this feed restriction regime arrested reproductive development and affected factors associated with energy balance purported to play a role in initiating reproductive development within 2-4months after spawning.