Natural mortality of blue crab: Estimation and influence on population dynamics

The blue crab Callinectes sapidus supports one of the most important fisheries in the Chesapeake Bay and is the leading contributor to blue crab landings in the United States. Assessment and management of blue crab stocks has been hampered by a lack of estimates of natural mortality rates, a key parameter in assessment models. In Chapter 2, we demonstrate that the approach used for estimating natural mortality that had been used in past assessments was flawed, and provide justification for a superior alternative. In Chapter 3, we synthesize our current understanding of natural mortality rates in adult blue crab and provide a suite of estimates for the Chesapeake Bay stock. Our estimates were used in the 2005 assessment for this stock, and the methods and estimates can provide guidance for assessments of the same or other species. In addition to estimates of natural mortality for adult blue crab, the short turnover time in the stock makes it necessary to consider changes in natural mortality rates with size or age. Current assessment models use an annual time step, which smooths over the changes in natural mortality that occur during ontogeny. Some crabs reach an exploitable size within the first year of life, and smaller crabs are expected to have higher natural mortality rates. In addition, natural mortality is known to vary seasonally, being highest in Chesapeake Bay during the summer months when predators are most abundant and crabs are molting frequently. to include size-dependent mortality in more realistic population dynamics models, we estimated mortality rates of juvenile crabs through field experiments (Chapter 4). In 2005 and 2006, we estimated mortality rates of seven cohorts of hatchery-reared juveniles in two tidal marsh creeks along the York River, Virginia during the summer and fall. Juvenile mortality rates were orders of magnitude higher than current estimates of adult mortality rates and were highest in the summer. Our results reinforce concerns about the adequacy of current assessment models and provide estimates of mortality that can be used to guide future work

Progressive Metamorphism of Pelitic, Carbonate, and Basic Rocks in South-Central Connecticut

Guidebook for field trips in Connecticut: New England Intercollegiate Geological Conference 60th annual meeting, Yale University, New Haven, Connecticut, October 25-27, 1968: Trip D-

Eukaryotic Organisms in Proterozoic Oceans

The geological record of protists begins well before the Ediacaran and Cambrian diversification of animals, but the antiquity of that history, its reliability as a chronicle of evolution and the causal inferences that can be drawn from it remain subjects of debate. Well-preserved protists are known from a relatively small number of Proterozoic formations, but taphonomic considerations suggest that they capture at least broad aspects of early eukaryotic evolution. A modest diversity of problematic, possibly stem group protists occurs in ca 1800–1300 Myr old rocks. 1300–720 Myr fossils document the divergence of major eukaryotic clades, but only with the Ediacaran–Cambrian radiation of animals did diversity increase within most clades with fossilizable members. While taxonomic placement of many Proterozoic eukaryotes may be arguable, the presence of characters used for that placement is not. Focus on character evolution permits inferences about the innovations in cell biology and development that underpin the taxonomic and morphological diversification of eukaryotic organisms.Organismic and Evolutionary Biolog

Visitation to Cottonseed Storage Sites by Feral Swine and Evidence of Gossypol Exposure

Texas ranks first in U.S. cotton production, and southern Texas is a major region of production within the state. Within Kleberg County, for example, approximately 16,147 ha are planted in cotton annually, yielding approximately 68,200 bales, or 15,467 metric tons, of cotton (U.S. Department of Agriculture [USDA] 2009). Cotton producers have discovered new uses for cotton ginned by-products, such as hydro-mulch (Holt et al. 2005) used as a protein supplement for range livestock (DelCurto et al. 2000) and white-tailed deer (Odocoileus virginianus; Cooper 2006). Because of this, much of the materials are temporarily stored for later use

Promiscuous mating in feral pigs (\u3ci\u3eSus scrofa\u3c/i\u3e) from Texas, USA

Context. Feral pigs represent a significant threat to agriculture and ecosystems and are disease reservoirs for pathogens affecting humans, livestock and other wildlife. Information on the behavioural ecology of feral pigs might increase the efficiency and effectiveness of management strategies. Aims. We assessed the frequency of promiscuous mating in relation to oestrous synchrony in feral pigs from southern Texas, USA, an agroecosystem with a widespread and well established population of feral pigs. An association between multiple paternity of single litters and synchrony of oestrous may indicate alternative mating strategies, such as mateguarding. Methods. We collected gravid sows at nine sites in southern Texas during 2005–07. We used a panel of DNA microsatellite markers to estimate frequency of multiple paternity and the distribution of male mating among litters of feral pigs. Conception dates were determined by fitting average fetal crown–rump measurements within litters to expected fetal development relative to gestation time. Key results. We found evidence of multiple paternity in 21 of 64 litters (33%) from seven of nine sites sampled. Synchrony of oestrous did not influence promiscuous mating, as we found multiple paternity at sites with synchronous and asynchronous oestrous. Males sired from 8 to 11 offspring at three sites where \u3e10 litters were sampled. Mean litter size (5.4) was less than the best-fit value for the number of offspring, indicating that some males sired offspring with ≥2 females. Key conclusions. Feral pigs in Texas appear to be promiscuous under a range of demographic conditions, unlike wild boar and feral pigs in other regions. The ecological and behavioural factors affecting multiple paternity are not clear, but may include male–male competition, harassment avoidance, genetic benefits for offspring, response to macro-habitat conditions, or selection. Implications. A high incidence of sexual contact among individuals may increase the opportunity for diseases transmitted by oral or venereal routes, such as swine brucellosis and pseudorabies. In addition, fertility-control methods targeting males only are likely to be inefficient if female promiscuity is high; methods targeting females or both sexes jointly may be more effective

Promiscuous mating in feral pigs (\u3ci\u3eSus scrofa\u3c/i\u3e) from Texas, USA

Context. Feral pigs represent a significant threat to agriculture and ecosystems and are disease reservoirs for pathogens affecting humans, livestock and other wildlife. Information on the behavioural ecology of feral pigs might increase the efficiency and effectiveness of management strategies. Aims. We assessed the frequency of promiscuous mating in relation to oestrous synchrony in feral pigs from southern Texas, USA, an agroecosystem with a widespread and well established population of feral pigs. An association between multiple paternity of single litters and synchrony of oestrous may indicate alternative mating strategies, such as mateguarding. Methods. We collected gravid sows at nine sites in southern Texas during 2005–07. We used a panel of DNA microsatellite markers to estimate frequency of multiple paternity and the distribution of male mating among litters of feral pigs. Conception dates were determined by fitting average fetal crown–rump measurements within litters to expected fetal development relative to gestation time. Key results. We found evidence of multiple paternity in 21 of 64 litters (33%) from seven of nine sites sampled. Synchrony of oestrous did not influence promiscuous mating, as we found multiple paternity at sites with synchronous and asynchronous oestrous. Males sired from 8 to 11 offspring at three sites where \u3e10 litters were sampled. Mean litter size (5.4) was less than the best-fit value for the number of offspring, indicating that some males sired offspring with ≥2 females. Key conclusions. Feral pigs in Texas appear to be promiscuous under a range of demographic conditions, unlike wild boar and feral pigs in other regions. The ecological and behavioural factors affecting multiple paternity are not clear, but may include male–male competition, harassment avoidance, genetic benefits for offspring, response to macro-habitat conditions, or selection. Implications. A high incidence of sexual contact among individuals may increase the opportunity for diseases transmitted by oral or venereal routes, such as swine brucellosis and pseudorabies. In addition, fertility-control methods targeting males only are likely to be inefficient if female promiscuity is high; methods targeting females or both sexes jointly may be more effective

Comparison of two approaches for estimating natural mortality based on longevity

Vetter (1988) noted that her review of the estimation of the instantaneous natural mortality rate (M) was initiated by a discussion among colleagues that identified M as the single most impor ta nt but least well-estimated parameter in fishery models. A lthough much has been accomplished in the inter vening years, M remains one of the most difficult parameters to estimate in fishery stock assessments. A number of novel approaches using tagging and telemetry data provide promise for making reliable direct estimates of M for a given stock (Hearn et al., 1998 ; Frusher and Hoenig, 2001; Hightower et al., 2001; Latour et al., 2003; Pollock et al., 2004). However, such methods are often impracticable and fishery scientists must approximate M by using estimates made for other stocks of the same or similar species or by predicting M from features of the species’ life history (Beverton and Holt, 1959; Beverton, 1963; Alverson and Carney, 1975; Pauly, 1980; Hoenig, 1983; Peterson and Wroblewski, 1984; Roff, 1984; Gunderson and Dygert, 1988; Chen and Watanabe, 1989; Charnov, 1993; Jensen, 1996; Lorenzen, 1996)

Effects of Carbohydrate-Based and Protein-Carbohydrate Rations on Wild Bobwhite Nesting and Harvest Demographics

Northern bobwhite (Colinus virginianus) reproduction is a nutrient-intensive process. Arthropods are essential for breeding bobwhite hens and their offspring. Traditional supplemental feeding programs use corn and milo and typically neglect the protein needs of bobwhites. Commercial bobwhite rations are widely available but are seldom used in feeding programs due to high cost and lack of an appropriate supplement for field use. We compared the effect of a protein-carbohydrate ration (PC) to the effects of a carbohydrate only ration (CO) on: (1) bobwhite hen nesting demographics (clutch size, ordinal clutch initiation date, Mayfield nest survival), and (2) fall relative abundance (coveys moved/hr hunting). Nesting parameters for bobwhites based on a sample of 60 hens during the 2008 breeding season in South Texas were statistically similar based on overlap of 95% confidence intervals for both the PC and CO supplements. Mayfield nest success was high for both the PC ration (75.2%) and the CO ration (73.1%). Coveys moved during hunting (4.17 6 14 coveys/hr in pastures with CO feed and 4.2 6 12.5 coveys/hr in pastures with PC feed) did not differ during the 2008–2009 hunting season. The 2009 nesting season was a failure because all study animals died due to drought. Weekly Kaplan-Meier survival estimates of bobwhite hens were 6 times higher in 2008 than in 2009. The PC ration in our study provided no benefit to bobwhite populations or enhancement of wild bobwhite reproductive parameters over the CO ration. The additional cost of using PC over CO is not justified based on our results