Recovery of severely declining resource stocks often leads to enforced quotas or reduced human access to those resources. Predators, however, do not recognize such restrictions and may be attracted to areas of increased prey abundances where human extraction is being limited. Such targeting by predators may reduce or retard the potential recovery of depressed stocks. In the San Juan Islands, northern Puget Sound, USA, marine reserves were implemented to recover depressed fish populations. We examine the role of harbor seals Phoca vitulina in the San Juan Islands food web. We describe the temporal and spatial variability in their diet, emphasizing species for which reserves were established (rockfish Sebastes spp.) and other important depressed stocks, including salmon Oncorhynchus spp. and Pacific herring Clupea pallasii. During winter and spring, seals primarily consumed Pacific herring, Pacific sand lance Ammodytes hexapterus, northern anchovy Engraulis mordax, and walleye pollock Theragra chalcogramma. During summer/fall, adult salmonids composed > 50% of the diet and were particularly important in oddnumbered calendar years, when pink salmon O. gorbuscha spawn. Rockfish were not a primary prey species at any time of the year, suggesting that the abundance of alternative prey species may reduce predation pressure and provide a critical buffer to rockfish predation. The importance of considering increased visitation by marine predators to areas where potential prey are enhanced through restrictions on human extractions should be considered when modeling the efficacy of quotas and reduced access areas, such as marine reserves.
Unbiased estimates of mountain goat (Oreamnos americanus) populations are key to meeting diverse harvest management and conservation objectives. We developed logistic regression models of factors influencing sightability of mountain goat groups during helicopter surveys throughout the Cascades and Olympic Ranges in western Washington during summers, 2004–2007. We conducted 205 trials of the ability of aerial survey crews to detect groups of mountain goats whose presence was known based on simultaneous direct observation from the ground (n = 84), Global Positioning System (GPS) telemetry (n = 115), or both (n = 6). Aerial survey crews detected 77% and 79% of all groups known to be present based on ground observers and GPS collars, respectively. The best models indicated that sightability of mountain goat groups was a function of the number of mountain goats in a group, presence of terrain obstruction, and extent of overstory vegetation. Aerial counts of mountain goats within groups did not differ greatly from known group sizes, indicating that under‐counting bias within detected groups of mountain goats was small. We applied Horvitz‐Thompson‐like sightability adjustments to 1,139 groups of mountain goats observed in the Cascade and Olympic ranges, Washington, USA, from 2004 to 2007. Estimated mean sightability of individual animals was 85% but ranged 0.75–0.91 in areas with low and high sightability, respectively. Simulations of mountain goat surveys indicated that precision of population estimates adjusted for sightability biases increased with population size and number of replicate surveys, providing general guidance for the design of future surveys. Because survey conditions, group sizes, and habitat occupied by goats vary among surveys, we recommend using sightability correction methods to decrease bias in population estimates from aerial surveys of mountain goats.
a b s t r a c tWe consider problems in finite-sample inference with two-step, monotone incomplete data drawn from N d (µ, ), a multivariate normal population with mean µ and covariance matrix . We derive a stochastic representation for the exact distribution of µ, the maximum likelihood estimator of µ. We obtain ellipsoidal confidence regions for µ through T 2 , a generalization of Hotelling's statistic. We derive the asymptotic distribution of, and probability inequalities for, T 2 under various assumptions on the sizes of the complete and incomplete samples. Further, we establish an upper bound for the supremum distance between the probability density functions of µ and µ, a normal approximation to µ.
Blood and fecal samples collected from 97 free-ranging mule deer (Odocoileus hemionus), from four distinct herds during the spring of 2000 or 2001 in eastern Washington, US, were tested for exposure to selected pathogens, concentrations of trace elements, and presence of parasites in feces. Antibodies were detected to the following: Leptospira interrogans serovar Bratislava (4%), Leptospira interrogans serovar Canicola (1%), Leptospira interrogans serovar Grippotyphosa (13%), Bovine viral diarrhea virus 1 (57%), Bovine respiratory syncytial virus (71%), Infectious bovine rhinotracheitis virus (51%), Bovine parainfluenza virus 3 (61%), Bluetongue virus (25%), and Epizootic hemorrhagic disease virus (25%); 3 of 63 (5%) samples had antibody to Neospora spp. All samples tested for antibody to Brucella abortus and L. interrogans serovar Icterohaemorrhagiae, L. interrogans serovar Pomona, and L. interrogans serovar Hardjo samples were negative. Trace element concentrations from 97 sera were deficient for selenium (17%), copper (19%), iron (34%), calcium (3%), and phosphorus (2%) compared with thresholds established for domestic livestock. Parasites detected in 97 fecal samples included dorsal-spined larvae (probably Parelaphostrongylus sp.) (40%), abomasal nematode eggs (1%), Capillaria sp. eggs (1%), Nematodirus sp. eggs (26%), Moniezia sp. eggs (1%), and Eimeria sp. (2%).
We examined the effects of hatchery rearing on FL, weight, egg size, fecundity, relative fecundity, and reproductive mass of female spring Chinook Salmon Oncorhynchus tshawytscha from a population that had been in captivity for 0 (natural‐origin), 18 (hatchery‐origin), and 48 (captive‐reared broodstock) months. Age‐4 captive‐reared broodstock females that were reared for their entire life in the hatchery environment had significantly lower mean FL, weight, fecundity, relative fecundity, and reproductive mass, but had significantly larger eggs than age‐4 females from the other groups after correcting for body size. Hatchery‐origin females had significantly lower fecundity than natural‐origin fish. Our findings illustrate a phenomenon of lower overall reproductive potential for hatchery‐reared fish in the form of reduced fecundity that decreases as time spent in the hatchery environment increases. We also observed that progeny of captive‐reared broodstock parents, released as smolts and recaptured as returning age‐4 adults, have a size and fecundity distribution that is similar to the hatchery‐origin adults, suggesting that the decrease in fecundity was not a genetically linked trait.
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