Multiple use of water: integration of fish culture and tree growing

Red tilapia (hybridOreochromis mossambicus x O. urolepis hornorum) were raised in pulsed flow irrigation systems in which water subsequently used to irrigate mesquite trees (Prosopis granulosa).The increase in height and stem base area was significantly greater (P<0.001) in mesquite trees irrigated with water from the fish culture facility than in mesquite trees irrigated with well water. Trees irrigated with water from the fish facility could be sold after about six months for prices ranging from $5.50 to $8.50. Trees irrigated with well water took twice as long to reach a marketable size.The Unit is jointly sponsored by the US Fish and Wildlife Service, Arizona Game and Fish, and the University of Arizona.     

Economic feasibility of introducing pulsed‐flow aquaculture into the irrigation system of cotton farms in Arizona

Abstract

The objective was to evaluate the economic feasibility of introducing fish culture into irrigated cotton production on farms in central Arizona. Water as a production variable was calculated only for the additional quantity required to keep water in the ditches during the growing season for fish. Raising tilapia in pulsed‐flow culture systems on Arizona cotton farms is economically feasible. Production function estimates indicate that profits can be increased through additional use of feed. At any ditch capacity, a density of six fish/m³ provided the optimal economic results, as the value of marginal product (VMP) equalled the price of fingerlings stocked/m³. This optimum fish production scenario would increase the net income for a typical irrigated cotton farm by 7 per cent. Increasing the initial size of the fingerlings improved the percentage of fish reaching marketable size and perhaps will increase economic returns, a question to be studied by future research.     

Production of Channel Catfish Ictalurus punctatus in Flowing Agricultural Waters in Arizona

Catfish were cultivated in 0.3 m³ site-specific cages built for fish culture in irrigation ditches. Poor growth (239 g ± 4.2) in 1989 was probably due to velocity of water and variability of fish size at stocking. Addition of baffles to the cages and hand grading of fish eliminated these problems in 1990. A power failure near the middle of the 1990 growing season forced the brief move of the fish from the ditch to a pond. Catfish reached an average weight of 465 g in 1990 over roughly the same growing season as in 1990. Before the cages were moved, fish at lower densities had significantly higher growth (588 ± 3, 515 ± 3) than those at higher densities (396 ± 4.6, 334 ± 4). However, at the end of the experiment, growth was not significantly different between densities (P > 0.05). Perhaps stress to fish caused by moving cages obliterated the previous density differences in growth.     

Farmers’ unconscious incorporation of sexually-produced genotypes into the germplasm of a vegetatively-propagated crop (Oxalis tuberosa Mol.)

Clonal propagation and sexual reproduction have diametrically opposite effects on the genetic diversity of crops, permitting, respectively, the conservation of existing genotypes or the creation of new diversity. Oxalis tuberosa Mol. (“oca”) exhibits a heteromorphic self-incompatibility system and is traditionally propagated clonally but is capable of sexual reproduction. In this study we investigated the influence of sexual reproduction on the in situ genetic diversity of a vegetatively propagated crop, taking oca as a model plant. The occurrence of sexual reproduction in natural conditions and its use by farmers were studied through surveys and interviews, while the effect of sexual reproduction on the in situ genetic diversity was evaluated using microsatellite analysis. Plantlets issuing from sexual reproduction were encountered in five of the nine visited communities. The interviews indicated that six out of the nine interviewed farmers were likely, albeit unconsciously, incorporating clonal lineages issuing from sexual reproduction into their varieties. The microsatellite analysis indicated a strong effect of such incorporations on the genetic diversity of the plant varieties. Assignment tests confirmed the allogamy of oca. “Complex varieties”, made up of individuals exhibiting genetically differentiated genotypes, were most likely the result of recent crossing. Unconscious incorporation of new genotypes into the cultivated oca germplasm is therefore highly likely, raising the question of its potential occurrence in other vegetatively propagated crops. These findings could have an important effect on the adaptive potential of oca, especially in light of the genetic erosion that threatens the crop.     

Optimum Density of Red Tilapia Oreochromis mossambicus×O. urolepis hornorum in a Pulsed-Flow Culture System

Abstract.— Densities of 9 tilapia (hybrid Oreochromis mossambicus × O. urolepis hornorum)/m³ gave the highest production among five densities (1, 3, 6, 9, and 12 fish/m³) tested in a pulsed-flow culture system. Culture of fish in irrigation ditches may have great potential for integrating fish farming with irrigated agriculture. Each 1,000 meters of ditch could potentially produce up to 1,400 kg of tilapia during a 112-d growing season.     

Growth response of indigenous and exotic carp species to different protein sources in pelleted feeds

Three indigenous carp species, Catla catla (Ham.), Labeo rohita (Ham.) and Cirrhinus mrigala (Ham.), and two exotic carp species, Cyprinus carpio L. and Hypophthalmichthys molitrix (Val.), were stocked together at a total density of 6000 fish ha^-1 in the ratio of 11:22:14:14:11, respectively. Three pelleted feeds, maize gluten (MG), cotton seed (CS) and fish meal (FM), were fed at 5% of the body weight of fish per day. The crude protein content of each feed was different. Growth rates for exotic species were significantly higher (P < 0.05) on all feeds than growth of indigenous species. The best growth for both exotic and indigenous carps was achieved on fish meal. Supplemental feeds made from locally available materials can enhance fish culture in Pakistan.     

Development and use of microsatellite markers for genetic diversity analysis of cañahua (<Emphasis Type="Italic">Chenopodium pallidicaule</Emphasis> Aellen)

Cañahua (Chenopodium pallidicaule Aellen) is a poorly studied, annual subsistence crop of the high Andes of South America. Its nutritional value (high in protein and mineral content) and ability to thrive in harsh climates make it an important regional food crop throughout the Andean region. The objectives of this study were to develop genetic markers and to quantify genetic diversity within cañahua. A set of 43 wild and cultivated cañahua genotypes and two related species (Chenopodium quinoa Willd. and Chenopodium petiolare Kunth) were evaluated for polymorphism using 192 microsatellite markers derived from random genomic cañahua sequences produced by 454 pyrosequencing of cañahua genomic DNA. Another 424 microsatellite markers from C. quinoa were also evaluated for cross-species amplification and polymorphism in cañahua. A total of 34 polymorphic microsatellite marker loci were identified which detected a total of 154 alleles with an average of 4.5 alleles per marker locus and an average heterozygosity value of 0.49. A cluster analysis, based on Nei genetic distance, clearly separated from wild cañahua genotypes from the cultivated genotypes. Within the cultivated genotypes, subclades were partitioned by AMOVA analysis into six model-based clusters, including a subclade consisting sole of erect morphotypes. The isolation by distance test displayed no significant correlation between geographic collection origin and genotypic data, suggesting that cañahua populations have moved extensively, presumably via ancient food exchange strategies among native peoples of the Andean region. The molecular markers reported here are a significant resource for ongoing efforts to characterize the extensive Bolivian and Peruvian cañahua germplasm banks, including the development of core germplasm collections needed to support emerging breeding programs.