The Effect of Understocking Density of Channel Catfish Stockers in Multiple-Batch Production

A multiple-batch study was conducted using stocker catfish (0.09 kg/fish) and carryover fish (0.39 kg/fish) to look at the effects of different stocker densities on fish production. Twelve 0.1-ha ponds were stocked with 7,400; 11,120; or 14,825 stockers/ha, and equal weights of carryover fish (2,268 kg/ha). Fish were fed once daily to apparent satiation with a 32% protein floating feed and aerated with a single 0.37-kW electric paddlewheel aerator. No significant differences were detected for gross, net, and net daily yields, growth (g/d), or survival. Sub-marketable yield (<0.57 kg) increased as stocking density increased. However, marketable yields (≥0.57 kg) were not affected by density. Carryover fish in high-density ponds had a significantly lower (P < 0.05) mean weight at harvest, but mean stocker weight was not different across densities. Economic analysis found breakeven prices increased and net returns decreased with increased stocking density when sub-marketable fish were not considered as revenue. The study indicated the possibility that stockers compete with large carryover fish, particularly at higher densities.     

A new collection of wild populations of Capsicum in Mexico and the southern United States

An exploration and collection mission for wild populations of Capsicum was carried out in the fall of 2006 and 2007, in 13 Mexican states and in the U.S. states of Arizona and Texas. The aim of this collection was to expand the number of accessions of wild chile pepper (Capsicum annuum var. glabriusculum and Capsicum frutescens) that are publicly available for research in plant improvement and for subsequent use in an inquiry into the domestication of C. annuum. While Mexico and the United States National Plant Germplasm System both have germplasm repositories INIFAP—Instituto Nacional de Investigaciones Forestales—Agrícolas y Pecuarias and USDA GRIN—United States Department of Agriculture’s Genetic Resources Information Network) with accessions of C. annuum var. glabriusculum, the very limited number available, their age, and/or validity of the information attached to many accessions do not allow for extensive research. Four hundred and sixty-six plants were sampled over two field seasons, of which copies of the collection reside in both UAA and at UC Davis. Given the current environment with the intellectual property of varieties of crop plants and, particularly, the extreme restrictions affecting explorations and the official procuring and sharing of germplasm across national borders, this U.S.—Mexico collaboration is one of the few examples of joint U.S.—Mexico germplasm collection efforts.