Size-selective mortality during freshwater and marine life stages of steelhead related to freshwater growth in the Skagit River, Washington

Wild steelhead trout, Oncorhynchus mykiss, in the Puget Sound are currently in decline, and very little is known about the early life history of these threatened fish. This study evaluated consequences of early growth and survival to smolt or adult stages in different precipitation zones of the Skagit River Basin, Washington. The objectives of this study were to determine whether significant size-selective mortality (SSM) in wild steelhead could be detected between freshwater stages and returning adults; and if so, how the magnitude of SSM varied among juveniles rearing in different precipitation zones (snow and mixed rain-snow). Wild steelhead were sampled as juveniles, smolts, and adults, and scales were measured to compare back-calculated size distributions and growth rates of rearing juveniles with individuals that survived from an earlier life stage to the smolt and adult stages. Back-calculated size-at-annulus comparisons indicated that steelhead in the snow zone were significantly larger at annulus-1 than those in the mixed zone. Steelhead sampled as adults were significantly larger than those sampled as juveniles at annuli-1, -2, and -3, and larger than those sampled as smolts at annuli-2 and -3, Steelhead sampled as smolts were larger than those sampled as juveniles at annuli-1 and -2, but smolts and juveniles were the same size at annulus-3. The disparity in size-at-age-2 and -3 between steelhead sampled at earlier and later life stages suggested that fast growth during the second or third freshwater growing seasons was vitally important for survival to adulthood, and that both freshwater and marine survival could be attributed, in part, to size attained at earlier life stages in freshwater. Efforts for recovery of threatened Puget Sound steelhead could benefit by considering SSM in freshwater environments, and identifying factors that limit growth during early life stages

Algenkweek met natuurlijk water en water uit het visbassin

Het Centrum voor Schelpdier Onderzoek wil het mogelijk maken om op kleine schaal mossel- en oesterzaad te kweken in de vorm van een kleine hatchery. Daarnaast is het CSO geïntresseerd in het gebruik van water uit het visbassin van een tarbotkwekerij als mogelijk voedingsmedium voor het kweken van algenculturen. Als blijkt dat het water uit het visbassin geschikt is als voedingsmedium en het minder tijd kost dan het maken van de chemische samenstelling kan overwogen worden dit water te gaan gebruiken

Integrating social knowledge and physical cues when judging the attractiveness of potential mates

Although many women find masculine men physically attractive, the perception that such men are prone to infidelity may limit their appeal as romantic partners. To explore this issue, we first investigated the interplay between the effects of men's face shape (masculinity versus femininity) and social knowledge of men's behavior in previous romantic relationships (faithful versus unfaithful) on women's judgments of men's attractiveness. Analyses suggested that the extent to which women rated masculine men to be more attractive than feminine men was significantly greater when judging men labeled as faithful than when judging men labeled as unfaithful. In a second experiment, we obtained similar results when the women in our study were instructed to imagine they were on a date with each of the men and that, while on the date, they observed him either flirting or not flirting with another woman. These interactions suggest that social knowledge about men's behavior in romantic relationships can offset one of the costs that women associate with choosing a masculine mate, increasing the appeal of masculine men. More fundamentally, these findings suggest integration of social knowledge and information from facial cues in women's attractiveness judgments

Sociosexuality predicts women's preferences for symmetry in men's faces

Although men displaying cues of good physical condition possess traits that are desirable in a mate (e.g., good health), these men are also more likely to possess antisocial characteristics that are undesirable in a long-term partner (e.g., aggression and tendency to infidelity). How women resolve this trade-off between the costs and benefits associated with choosing a mate in good physical condition may lead to strategic variation in women's mate preferences. Because the costs of choosing a mate with antisocial personality characteristics are greater in long- than short-term relationships, women's sociosexuality (i.e., the extent to which they are interested in uncommitted sexual relationships) may predict individual differences in their mate preferences. Here we investigated variation in 99 heterosexual women's preferences for facial symmetry, a characteristic that is thought to be an important cue of physical condition. Symmetry preferences were assessed using pairs of symmetrized and original (i.e., relatively asymmetric) versions of 10 male and 10 female faces. Analyses showed that women's sociosexuality, and their sociosexual attitude in particular, predicted their preferences for symmetry in men's, but not women's, faces; women who reported being more interested in short-term, uncommitted relationships demonstrated stronger attraction to symmetric men. Our findings present new evidence for potentially adaptive variation in women's symmetry preferences that is consistent with trade-off theories of attraction