Raising Juveniles

This paper investigates how families make decisions about the education of juveniles. The decision problem is analyzed in three variations: a 'decentralized' scheme, in which the parents control the purse-strings, but the children dispose of their time as they see fit; a 'hierarchical' scheme, in which the parents can enforce a particular level of schooling by employing a monitoring technology; and the cooperative solution, in which the threat point is one of the two noncooperative outcomes. Adults choose which game is played. While the subgame perfect equilibrium of the overall game is Pareto-efficient when viewed statically, it may yield less education than the hierarchical scheme. Regulation in the form of restrictions on child labor and compulsory schooling generally affects both the threat point and the feasible set of bargaining outcomes, and families may choose more schooling than the minimum required by law.family decision-making, youth, human capital, bargaining

Survival and Growth of American Alligator (Alligator mississippiensis) hatchlings after artificial incubation and repatriation

Hatchling American Alligators (Alligator mississippiensis) produced from artificially incubated wild eggs were returned to their natal areas (repatriated). We compared artificially incubated and repatriated hatchlings released within and outside the maternal alligator’s home range with naturally incubated hatchlings captured and released within the maternal alligator’s home range on Lake Apopka, Lake Griffin, and Orange Lake in Florida. We used probability of recapture and total length at approximately nine months after hatching as indices of survival and growth rates. Artificially incubated hatchlings released outside of the maternal alligator’s home range had lower recapture probabilities than either naturally incubated hatchlings or artificially incubated hatchlings released near the original nest site. Recapture probabilities of other treatments did not differ significantly. Artificially incubated hatchlings were approximately 6% shorter than naturally incubated hatchlings at approximately nine months after hatching. We concluded that repatriation of hatchlings probably would not have long-term effects on populations because of the resiliency of alligator populations to alterations of early age-class survival and growth rates of the magnitude that we observed. Repatriation of hatchlings may be an economical alternative to repatriation of older juveniles for population restoration. However, the location of release may affect subsequent survival and growth

Comparative larval biology of three Macrobrachium species under controlled conditions

Three large sized Macrobrachium species-. viz. Macrobrachium rosenbergi;, M malcolmsonii and M gangelicum are available in Indian riverine systems. The study on the seed production and growout of these species are being carried out to develop technologies for commercial application. Hence, the knowledge on comparative larval biology of the three species is extremely important to give a new line for developing hatchery technology for large-scale seed production in different agro-climatic conditions. The present communication deals with comparative study of larval growth and seed production of the three larger species

Preliminary observations on the growth and survival of tiger prawn (Penaeus monodon Fabricius) postlarvae in pen-nurseries

In an attempt to ensure all-time availability of stocking materials of P. monodon Fabriciua, experiments have bean undertaken on a large scale in the lower Sunderbans area of West Bengal for growing the wild-caught post-larvae (10-12 mm) of the species to an advanced juvenile (35-45 mm) stage under semi-controlled conditions. Six nursery pens (0.1 ha each) have been installed in a large (60 ha) brackishwatar impoundment and stocked at the rate of 2.0-3.6 millions per hectare. Besides encouraging the growth of natural food, the postlarvae are fed with well balanced artificial diets having protein from both animal and plant origin. Encouraging results with high survival (upto 73%) end faster growth rates have been observed In some of the trial runs. Details of stocking density, growth rate, percentage survival and the feeding schedule etc. are presented and discussed. Various physico-chemical parameters recorded at regular intervals are also given

Fish Farms at Sea: The Ground Truth from Google Earth

In the face of global overfishing of wild-caught seafood, ocean fish farming has augmented the supply of fresh fish to western markets and become one of the fastest growing global industries. Accurate reporting of quantities of wild-caught fish has been problematic and we questioned whether similar discrepancies in data exist in statistics for farmed fish production. In the Mediterranean Sea, ocean fish farming is prevalent and stationary cages can be seen off the coasts of 16 countries using satellite imagery available through Google Earth. Using this tool, we demonstrate here that a few trained scientists now have the capacity to ground truth farmed fish production data reported by the Mediterranean countries. With Google Earth, we could examine 91% of the Mediterranean coast and count 248 tuna cages (circular cages >40 m diameter) and 20,976 other fish cages within 10 km offshore, the majority of which were off Greece (49%) and Turkey (31%). Combining satellite imagery with assumptions about cage volume, fish density, harvest rates, and seasonal capacity, we make a conservative approximation of ocean-farmed finfish production for 16 Mediterranean countries. Our overall estimate of 225,736 t of farmed finfish (not including tuna) in the Mediterranean Sea in 2006 is only slightly more than the United Nations Food and Agriculture Organization reports. The results demonstrate the reliability of recent FAO farmed fish production statistics for the Mediterranean as well as the promise of Google Earth to collect and ground truth data

Juvenile temperature regulation in Apis mellifera (Honey bee) and the impacts of brood temperature requirements on the colony

Little is known about the energetic costs to insects of raising young. Honey bees collectively raise young, or brood, through a series of complex behaviors that appear to accelerate and synchronize the timing of brood maturation. These include maintaining the brood nest at warmer and consistent temperatures and the exceptional activity of heater bees. The temperature at which juvenile insects are raised can profoundly affect their development. Apis mellifera (Honey bees) cope with temperature-dependent development via social behavior that maintains the relatively high and constant temperatures within the nest where the brood are raised. Yet juvenile honey bee development is complex and can be categorized into egg, larvae, pupating juveniles, and pupae. Honey bees use passive and active behaviors to maintain remarkably constant brood nest temperatures, from 33 to 35°C, across a wide range of ambient temperatures. In addition to these colony-scale behaviors, a small subset of nurse bees behaves as heater bees. Heater bees contract thoracic flight muscles to generate heat, but their thoraxes reach much higher temperatures than other bees responsible for brood care, ranging between 42 and 47°C. Heater bees focus their attention on incubating individual cells by moving among brood cells and regulating the temperatures of individual eggs, larvae, and pupae. We constructed four sets of experimental hives to explore the developmental temperatures at which each juvenile stage is maintained, the energetic costs of raising juveniles, and the cost of heater bees. One set allowed us to record the temperatures of undisturbed young in the brood nest area established by the colony. The second set was designed to estimate the numerical allocation of individuals to the heater bee task. The third set was intended to contain only brood, which eliminated foraging and allowed us to quantify stored honey use when rearing juveniles at 10 and 30°C. The final set was used to measure the respiration rates and energy expenditure of individual bees displaying resting, walking, heating, and agitated behavior. We first discovered that instead of simply maintaining brood nest areas at 33-35°C, honey bees provide extraordinarily precise but different temperatures for larvae and pupae. We found that the temperature at which heater bees regulate cells is above the overall average temperature range of the brood nest. Honey bees raised larvae at 36.38±0.02°C, substantially higher and with a narrower range than what has been reported for the brood nest, 33-35°C. Honey bees raised pupae at 35.18±0.04°C, also higher than the reported temperatures for the brood nest. We further explored brood development by characterizing the developing juveniles\u27 temperature profile throughout their entire 21-day developmental cycle. We found that eggs were maintained at 36.1 ± 0.03°C, larvae at 36.2 ± 0.02°C, pupating juveniles at 35.9 ± 0.03°C, and pupae at 35.8 ± 0.03°C. All stages were significantly different from all other stages, but importantly larvae were only 0.4°C different from pupae. We then conducted another experiment with brood frames without mature bees and in incubators at 34.5°C. Without nurse bees, the temperatures of eggs, larvae, and pupae were 34.4 ± 0.04°C, 34.7 ± 0.05°C, and 34.3 ± 0.04°C, with larvae different from all other stages, and a 0.3°C difference between larvae and pupae. When compared to the 1.2°C in Chapter 1, this 0.3°C difference suggests that heater bees may be a major driver of the differences between pupae and larvae. However, the 0.4°C difference between larvae and pupae in the second experiment reported in chapter 2, vs. the 0.3°C difference, suggests that the larvae themselves may be the major contributor to the temperature difference between the life stages. Either way, our results suggest honey bee development may involve far more precise temperature during the development of juveniles than previously known. And finally, to determine the cost of maintaining juveniles at these warmer and more consistent temperatures, we compared the honey used by brood-only experimental colonies with whole-colony measurements of honey storage in the literature. We estimated that raising brood costs colonies half of their annual energy budgets stored as honey, or approximately 43.7±0.9 kg·yr-1. We estimated that roughly 2% of colony individuals perform the task of heater bee. Respiration rates of heater bees (19 mW) were more than those of resting bees (8 mW) but similar to those of walking bees (20 mW) and about half of those that were agitated (46 mW). The energetic cost of heating was more than an order of magnitude lower than reported values for the energetic cost of flying. By integrating data from our experimental hives, we estimate that the annual cost of raising brood is quite high; however, we estimate that heater bee behavior and physiology, though extreme, may require only about 7% of the annual honey stored by a colony. Instead of simply maintaining brood nest areas at 33-35°C, honey bees provide extraordinarily precise but different temperatures for larvae and pupae. We do not know if these differences ultimately affect development, but they suggest that honey bees may exert far more precise control over the temperatures of their juveniles than previously known, which comes at a high cost at the colony level (macroeconomic), but a surprisingly low cost at the individual (microeconomic) heater bee level

Building and Managing a Tropical Fish Facility: A Do-It-Yourself Guide

At the core of most research in zoological disciplines, ranging from developmental biology to genetics to behavioral biology, is the ability to keep animals in captivity. While facilities for traditional model organisms often benefit from well-established designs, construction of a facility for less commonly studied organisms can present a challenge. Here, we detail the process of designing, constructing, and operating a specialized 10,000-liter aquatic facility dedicated to housing cichlid fishes for research purposes. The facility, comprising 42 aquaria capable of division into up to 126 compartments, a flow-through rack for juveniles, egg tumblers for eggs and embryos, and a microinjection setup, provides a comprehensive environment for all life stages of cichlid fishes. We anticipate that a similar design can be also used also for other tropical teleost fishes. This resource is designed to promote increased efficiency and success in cichlid fish breeding and research, thereby offering significant insights for aquatic research labs seeking to build or optimize their own infrastructures.Comment: 14 pages, 9 figures, 2 table