Habitat characteristics at bluegill spawning colonies in a South Dakota glacial lake

Abstract –  Bluegill ( Lepomis macrochirus ) primarily reproduce in spawning colonies. We assessed habitat characteristics at 15 bluegill spawning colonies in a South Dakota glacial lake. Nesting sites were visually identified and angling was used to verify the species of nesting fish. Habitat characteristics were measured at each nesting site and compared with those measured at 75 randomly selected sites. In Lake Cochrane, mean water depth of spawning colonies was 1.0 m. Of the 13 habitat characteristics measured, four (substrate type, substrate firmness, vegetation density and dissolved oxygen levels) were significantly different ( P  ≤ 0.05) between nesting and random sites. Every bluegill nest site contained gravel substrate, despite the availability of muck, sand and rock. Substrate firmness was indexed at 0-cm penetration and vegetation density was low at all nesting sites. Additionally, bluegills selected nesting locations with relatively moderate dissolved oxygen levels. Lake Cochrane bluegill nest sites consisted of shallow, gravel areas with short, low-density, live submergent Chara vegetation.     

Paleoindian seafaring, maritime technologies, and coastal foraging on California's Channel Islands

Three archaeological sites on California's Channel Islands show that Paleoindians relied heavily on marine resources. The Paleocoastal sites, dated between ~12,200 and 11,200 years ago, contain numerous stemmed projectile points and crescents associated with a variety of marine and aquatic faunal remains. At site CA-SRI-512 on Santa Rosa Island, Paleocoastal peoples used such tools to capture geese, cormorants, and other birds, along with marine mammals and finfish. At Cardwell Bluffs on San Miguel Island, Paleocoastal peoples collected local chert cobbles, worked them into bifaces and projectile points, and discarded thousands of marine shells. With bifacial technologies similar to those seen in Western Pluvial Lakes Tradition assemblages of western North America, the sites provide evidence for seafaring and island colonization by Paleoindians with a diversified maritime economy.     

Follow-up of mercury levels in fish,human hair and urine in the Madeira and Tapajós basins,Amazon, Brazil

Informal economy of gold mining has contaminated some important river basins in Amazon. Follow-up studies on critical compartments showed some areas with high Hg levels in fish as well as in human hair samples. Average Hg in piscivorous fish in the Madeira river itself was 846 ppb (N=284) with a maximum of 3921 ppb. Mercury in fish from non polluted areas in this basin shows high variability, even for single species. A seasonal variation in Hg content was observed, with higher values at the end of the dry season. In the upper Tapajós basin comparable values were found for fish but with a definite decreasing trend downstream. Average value for piscivorous fish in the whole Tapajós basin is 482 ppb (N=122) with a maximum value of 3770 ppb. Hair Hg was higher in fishing villages in the Tapajós (average: 17 ppm; with N=432 and maximum value of 176 ppm) than in the Madeira (average: 9 ppm; N=169; maximum 71 ppm), and data from some areas of the Tapajós suggest a decrease with time. Mercury was much higher in urine of goldshop workers in Santarém (low Tapajós) than in Alta Floresta (high Tapajbs) and show a decreasing trend in both cases, probably related to the significant decline in gold mining activities during the study period (1986–1994).     

Solvent effects on the crystallization behavior of milk fat fractions

The high- and medium-melting fractions of milk fat (HMF and MMF, respectively) were crystallized in the presence of various solvents, including the low-melting fraction of milk fat (LMF), canola oil (CO), hexane, and ethyl acetate. Choice of solvent was shown to have a strong influence on phase behavior and crystallization kinetics. Dilution and solubilization effects were observed for all the blends. More solids were formed in the HMF and MMF blends with LMF than with CO, and complexes were formed between the milk fat fractions possibly because of molecular complementarity. Solids were slightly higher for the more polar ethyl acetate than for hexane. Crystallization proceeded more rapidly in the presence of LMF and ethyl acetate than in the presence of CO and hexane, respectively. According to the Hildebrand equation, HMF and MMF were ideally soluble in LMF and CO. X-ray diffraction spectroscopy (XRD) revealed the existence of liquid-state structure in mixtures of HMF/CO, HMF/LMF, MMF/CO, and MMF/LMF. The observed liquid-state structure was reminiscent of liquid crystals. No differences were observed in the structure of the liquid phase between LMF- and CO-containing mixtures.