No abstract

Lack 18:125-128 (1967) proposed that clutch size in precocial species was regulated by nutrients available to females during breeding. Drent and Daan 68:225-252 (1980) proposed the individual optimization hypothesis, whereby individual state determines the optimal combination of breeding date and clutch size. Neither hypothesis accounts for variation in nutrients among females at the end of egg laying, strong right truncations in clutch size distributions, or the fact that many species with precocial young are determinate layers. One solution is that there is a maximum clutch size, above which the number of fledged young declines. We manipulated brood size in Black Brent geese to decouple brood size from maternal quality and produce broods larger than the natural maximum. We recaptured marked goslings to assess variation in prefledging survival as a function of brood size and we estimated relative prefledging survival of goslings using a Bayesian hierarchical approach. We considered effects of natural clutch size, brood size and their interaction on probability that we captured goslings at about 4 weeks of age. Prefledging survival declined with increasing brood size ([Formula: see text] = -0.53; 95% CI -0.91 to -0.16), while laid clutch size had little influence on prefledging survival ([Formula: see text] = -0.04; 95% CI -0.42 to 0.32). Despite declining per capita survival with increasing brood size, the most productive brood size was six goslings, which is greater than the typical maximum clutch size of five. Thus, reduced survival in large broods, by itself, is not the sole mechanism that limits maximum clutch size. We suggest elsewhere that incubation limitation and lower residual reproductive value for females tending larger broods may be other mechanisms limiting maximal clutch size in brent.

Lahontan cutthroat trout Oncorhynchus clarkii henshawi are listed as threatened under the U.S. Endangered Species Act. Populations inhabiting terminal lakes in the Great Basin of Utah and adjacent states face increasing salinity associated with increased anthropogenic use of water and climate change. We used tag recovery models and Markov chain–Monte Carlo methods to assess models of variation in annual survival and tag recovery rates for two genetic strains (Pilot Peak and Pyramid Lake) of Lahontan cutthroat trout stocked into Walker Lake, Nevada, from 1998 to 2008. The best‐performing model of annual survival and tag recoveries allowed recovery probability in the first year after release to differ from subsequent recovery rates. The best model contained an interaction between strain and total dissolved solids (TDS) for annual survival. That is, the annual survival of both strains declined as TDS increased, but the Pilot Peak strain was more sensitive to TDS than was the Pyramid Lake strain. The annual survival of fish from the Pilot Peak strain was higher than that of the Pyramid Lake strain at all but the highest TDS levels. Although TDS levels in 2005–2008 were too high to warrant continued stocking of cutthroat trout into Walker Lake, if flows into Walker Lake are increased sufficiently to return TDS levels to those of the late 1990s, the Pilot Peak strain should be stocked. Received August 24, 2011; accepted February 6, 2012