Leisure/Labor Tradeoffs: The Backward-Bending Labor Supply in Fisheries

Economists have understood that the open-access nature of fishing grounds can cause the long-run fishery supply to bend backward. There is also increasing speculation that fishermen respond to falling output price either by increasing or decreasing effort, depending on the circumstances. This suggests a short-run backward-bending supply of fishing labor. A dynamic, utility-theoretic model of fishermen's behavior is developed to address this possibility. The model highlights both contemporaneous and intertemporal trade-offs between labor and leisure. The model is tested and the results indicate that the short-run labor supply in fisheries may exhibit backward-bending properties. In addition, changes in current prices may trigger changes in expectations of future prices, causing potentially greater counterintuitive behavior. These results challenge many traditional regulatory strategies (e.g., output taxes) that address problems of open access.     

Green leaf volatiles enhance sex attractant pheromone of the tobacco budworm,Heliothis virescens (Lep.: Noctuidae)

Summary Components of the green leaf volatile complex (Z-3-hexenyl acetate andE-2-hexenyl acetate) were shown to enhance responses of tobacco budworm,Heliothis virescens, males to the sex attractant pheromone of conspecific females in the field. The results are discussed with regard to green leaf volatiles which enhance the attractant pheromone of a cohabiting species, and serve as attractants of a parasitoid of conspecific larvae.     

Systemic retention of ingested cantharidin by frogs

Summary Frogs(Rana pipiens) fed on blister beetles (Meloidae) or cantharidin, retain cantharidin systemically. After cessation of feeding, they void the compound relatively quickly. Systemic cantharidin does not protect frogs against ectoparasitic feeding by leeches(Hirudo medicinalis) or predation by snakes(Nerodia sipedon). As suggested by our data, and from reports in the early literature, ingestion of cantharidin-containing frogs can pose a health threat to humans.Paper no. 95 of the seriesDefense Mechanisms of Arthropods; no. 94 is LaMunyon & Eisner, Psyche (in press)     

Growth and moulting of Neomysis integer (Crustacea: Mysidacea)

The growth and moulting of Neomysis integer (Leach) was investigated in the field and the laboratory. In the Ythan estuary, Aberdeenshire, Scotland, monthly samples taken from November 1976 to October 1978 revealed that the summer generation juveniles and mature individuals grew at a rate of 4 to 5 mm and 1 to 2 mm monthly, respectively. The winter generation had a growth rate of 3 to 4 mm monthly for juveniles and about 1 mm for mature individuals; during the winter there was a period of 3 mo when growth was almost completely stopped. Mysids reared in the laboratory on Artemia sp. nauplii had an average daily growth rate of 0.06 mm at 9°C and 0.09 mm at 16°C. The growth factors of N. integer ranged from 3 to 17% for mature and immature individuals, respectively. Intermoult periods ranged from 3 to 7 d in immature mysids to 12 to 18 d in mature mysids. Average laboratory growth curves calculated from information on growth factors and intermoult periods indicate that at 9°C (winter generation) it takes N. integer 277 d to grow to be a 15 mm mature individual, whereas at 16°C (summer generation) it takes 188 d. N. integer moults 24 times as it grows from a juvenile to a mature individual.     

Why do honey bees have dialects?

Summary The indication of distance in the honey bee dance-the number of meters signified by each waggle-varies by more than a factor of ten among geographic races. Experiments in which artificial swarms were offered a choice of nest boxes indicate that A. m. carnica, the long-distance German race, clearly prefers larger and more distant cavities than the intermediate-dialect Italian race, ligustica. From these results on preferred dispersal distance and cavity size, combined with a general trend among the many races of honey bee toward dialects adapted for indicating longer distances occurring in colder latitudes, I propose that the dialect is probably an adaptation to each race's typical foraging range. That range is in large part a necessary consequence of population size, which in turn is determined by the thermal load imposed on clusters by winters in different climates.     

Amino acid uptake and respiration by marine heterotrophs

The concentration and turnover of dissolved free amino acids were measured in samples from 25 and 100 m on three occasions at a station 6 miles off the California (USA) coast. Individual amino acid concentrations varied from undetectable (<0.05 g/l) to 3 g/l, the total amino acid concentration from 1.8 to 8.5 g/l. The greater concentration of total amino acids was always found at 25 m. The predominant amino acids were serine, lysine, aspartate, glutamate and alanine; reliable analyses could not be made for glycine because of a high blank. For the 10 individual amino acids studied, the rate of heterotrophic turnover ranged from undetectable to 1.2 g/l day^-1; serine, aspartate, alanine and glutamate showed the highest rates. In samples from 25 m, the rates were 15 to 20 times higher than those taken from 100 m. The total calculated flux of the amino acids studied varied from 0.015 to 3.2 g/l day^-1 and amounted to 1–10% of photosynthetic carbon dioxide fixation.     

Tsuga canadensis (L.) Carr. mortality will impact hydrologic processes in southern Appalachian forest ecosystems.

Eastern hemlock (Tsuga canadensis (L.) Carr.) is one of the principal riparian and cove canopy species in the southern Appalachian Mountains. Throughout its range, eastern hemlock is facing potential widespread mortality from the hemlock woolly adelgid (HWA). If HWA-induced eastern hemlock mortality alters hydrologic function, land managers will be challenged to develop management strategies that restore function or mitigate impacts. To estimate the impact that the loss of this forest species will have on the hydrologic budget, we quantified and modeled transpiration over a range of tree sizes and environmental conditions. We used heat dissipation probes, leaf-level gas-exchange measurements, allometric scaling, and time series modeling techniques to quantify whole-tree and leaf-level transpiration (E(L)) of eastern hemlock. We monitored trees ranging from 9.5 to 67.5 cm in diameter along a riparian corridor in western North Carolina, USA during 2004 and 2005. Maximum rates of daily tree water use varied by diameter and height, with large trees transpiring a maximum of 178-186 kg H2O x tree(-1) x d(-1). Values of E(L) could be predicted from current and lagged environmental variables. We forecasted eastern hemlock E(L) for inventoried stands and estimated a mean annual transpiration rate of 63.3 mm/yr for the hemlock component, with 50% being transpired in the winter and spring. In typical southern Appalachian stands, eastern hemlock mortality would thus reduce annual stand-level transpiration by approximately 10% and reduce winter and spring stand-level transpiration by approximately 30%. Eastern hemlock in the southern Appalachians has two distinct ecohydrological roles: an evergreen tree that maintains year-round transpiration rates and a riparian tree that has high transpiration rates in the spring. No other native evergreen in the southern Appalachians will likely fill the ecohydrological role of eastern hemlock if widespread mortality occurs. With the loss of this species, we predict persistent increases in discharge, decreases in the diurnal amplitude of streamflow, and increases in the width of the variable source area.     

Sampling design trade-offs in occupancy studies with imperfect detection: examples and software.

Researchers have used occupancy, or probability of occupancy, as a response or state variable in a variety of studies (e.g., habitat modeling), and occupancy is increasingly favored by numerous state, federal, and international agencies engaged in monitoring programs. Recent advances in estimation methods have emphasized that reliable inferences can be made from these types of studies if detection and occupancy probabilities are simultaneously estimated. The need for temporal replication at sampled sites to estimate detection probability creates a trade-off between spatial replication (number of sample sites distributed within the area of interest/inference) and temporal replication (number of repeated surveys at each site). Here, we discuss a suite of questions commonly encountered during the design phase of occupancy studies, and we describe software (program GENPRES) developed to allow investigators to easily explore design trade-offs focused on particularities of their study system and sampling limitations. We illustrate the utility of program GENPRES using an amphibian example from Greater Yellowstone National Park, U.S.A.     

Structural organisation,transfer and biological fate of endosymbiotic bacteria in gutless oligochaetes

From differences in size and structure, it appears there are two species of gram-negative bacteria in the gutless oligochaetes Phallodrilus leukodermatus and P. planus from Bermuda. A non-random, differentiated and consisten distribution pattern of the extracellular bacteria along the length of the worm's body underlines the regulated nature of the bacterial colonization. This emerges also from studies on the transfer of the bacteria between host generations: exceptional for oligochaetes, eggs are deposited singly in a sticky mucus sheath and not together in a cocoon. They become infected immediately at oviposition, apparently by intrusion from large stores of bacteria in a genital pad abutting the female pores. During ontogenesis, a balance is established between extracellular, active bacteria and intracellular lytic forms enclosed in vacuoles by the epidermal cells. In early developmental stages, lytic bacteria prevail, but older worms harbour mainly extracellular prokaryotes underneath their cuticle. The thick epidermis/cuticle complex is differentiated in regular zones with a progressive trend towards enclosing and digesting bacteria intracellularly in the deeper layers. These are the first results on the transfer and biological fate of endosymbiotic bacteria living in animals from sulfide biotopes.     

Comparison of some homogeneity tests in analysis of over-dispersed binomial data

This paper compares the procedures based on the extended quasi-likelihood, pseudo-likelihood and quasi-likelihood approaches for testing homogeneity of several proportions for over-dispersed binomial data. The type I error of the Wald tests using the model-based and robust variance estimates, the score test, and the extended quasi-likelihood ratio test (deviance reduction test) were examined by simulation. The extended quasi-likelihood method performs less well when mean responses are close to 1 or 0. The model-based Wald test based on the quasi-likelihood performs the best in maintaining the nominal level. The score test performs less well when the intracluster correlations are large or heterogeneous. In summary: (i) both the quasilikelihood and pseudo-likelihood methods appear to be acceptable but care must be taken when overfitting a variance function with small sample sizes; (ii) the extended quasi-likelihood approach is the least favourable method because its nominal level is much too high; and (iii) the robust variance estimator performs poorly, particularly when the sample size is small.