A primary parameter in the assessment of the viability of a population is its effective population size (Ne). Allozyme analysis of four groups of fishes provided data on linkage disequilibrium, which were then used to estimate Ne. The groups included hatchery samples of juvenile white seabass, Atractoscion nobilis, juvenile rainbow trout, Oncorhynchus mykiss, from the Shasta Hatchery, and juvenile chinook salmon, O. tshawytscha, from the Coleman National Fish Hatchery. The fourth sample consisted of juvenile chinook salmon from the threatened winter run in the upper Sacramento River. The groups of fish were chosen to represent different applications of the methodology to conservation of fishes. For a variety of reasons. Ne may be considerably lower than census counts of fish present in the parental populations. The Ne of the hatchery broodstock that produced the sample of juvenile white seabass was estimated to be approximately 10, although 25 adult white seabass were present in a mass spawning tank. Ne estimates for the parental populations of the Shasta and Coleman Hatchery samples were 35.8 and 132.5, respectively. The actual number of fish spawned at the Shasta Hatchery was approximately 40, whereas nearly 10,000 salmon were spawned at the Coleman Hatchery. The threatened winter run of chinook salmon had an estimated Ne of 85.5 and an approximate run size of 2000 salmon. The method of estimating effective population size from linkage disequilibrium data appears to result in realistic estimates of effective population size when adequate sample size and a sufficient number of polymorphic loci are available.

Beef steers were fed in two phases to compare the effects of diet and intake on growth and cellularity of visceral organs. During the growing phase (237 to 327 kg), steers were fed either a high (C) or low (F) concentrate diet. Diet F was available ad libitum (FA), whereas diet C was available either ad libitum (CA) or on a limited basis (CL) to match live weight gains of the FA group. During the finishing phase (327 to 481 kg), all steers received diet C either ad libitum (CA-CA, CL-CA, and FA-CA) or restricted (CL-CL and FA-CL) to 70% of the intakes of corresponding CA steers. Marked nutritional effects on liver growth (e.g., -25 and -15% in CL and FA, respectively, relative to CA) were due mainly to changes in cell size (i.e., protein:DNA), with smaller changes in cell numbers (i.e., DNA). Hyperplasia and hypertrophy played a role in growth of the forestomachs, although cell numbers and sizes tended to change in opposite directions, limiting magnitudes of changes in organ mass. Protein synthetic capacity (i.e., RNA) varied as well, often in parallel with cell number. This result differed from that observed in intestines, which maintained constant cell sizes but underwent marked changes in cell number. For liver, amounts of absorbed nutrients seemed to be the main factor driving hypertrophy. The organs of the gastrointestinal tract responded to physical and chemical signals, as shown by the effects of dietary fiber on growth of the forestomachs and intestines. Forestomachs responded mainly to diet fiber content, whereas the intestines responded to diet type and nutrient supply. Feeding programs for beef animals often include changes in diet type and periods of feed limitation, and these in turn affect visceral organ growth and metabolism. Because visceral organs are a major contributor to whole-body energy expenditures, factors affecting these tissues must be understood. This study supports the concept that workload determines organ size, but dietary factors influencing workload clearly vary for each organ.

No abstract

1992. Tests of genetic stock identification using coded wire tagged fish. Can. 1. Fish. Aquat. Sci. 49: 1507-4 51 7.Genetic Stock Identification (GSI) uses allozyme variation to determine the composition of mixed-stock fisheries.The GSB method was tested using real fishery data. We report, for the first time in the primary literature, results of tests of GSB in which source stock and ocean-caught mixture samples were separately obtained and the mixture composition was known exactly because the fish used were marked by Coded Wire Tags (CWTs). The accuracy of GS! and its dependence on the quality of genetic data were studied by computer experiments. Rare alleles, which could result from poor sampling procedures, can lead to significant estimation errors. Estimation accuracy depended on the concordance between stocks present in the baseline data and the mixture sample and on the nurriber of loci used in the analysis. Two methods for computing the contributions of groups of source stocks were found to be comparable under most, but not all, conditions. In a blind test of GSI, stock group composition estimates had absolute errors of less than 3%. This suggests that the GSi method can produce accurate stock contribution estimates using real fishery data, La rnethode d'identification genktique des stocks se sert de la variation des allozymes pour etablir la composition de pecheries pluristocks. Les auteurs l'ont appliquke 3 des donnkes actuelles sur la peche et presentent les rksultats obtenus pour la paemi6re fois dans une publication primaire. Ils ont pu identifier les echantillons tires d'un stock source et les 6chantilBons melanges captures en mer, et ont determine exactement la composition de ceux-ci car les poissons portaient des etiquettes metalliques codees. Les auteurs ont aussi etudik la precision de cette methode d'identification et sa dependance sur la quasite des donnkes genetiques par l'entaemise d'experiences informatiques. kes all$les rares, qui sont peut-etre le resultat de rngthodes d%chaatillonnage inadkquates, peuvent &re a la source d'importantes erreurs d'estimation. La pr6cision de I'estimation depndait de I'accord entre, d'uwe part, les stocks represent& dans les donnees de base et les echantillons melanges et, d'autre part, le nombre de loci utilisks tors de I'analyse. Deux methodes de calcul de la contribution de groupes de stocks sources ont et6 identifiees comme equivalentes dans presque toutes les conditions. Lors d'une epreuve 2 I'insu de la rnkthode d'identification genetique, l'erreur absslue des estimations de la composition du groupe de stock etait inferieure a 3 %. Ceci porte 5 croire que cette methode peut donner des estimations precises de la contribution d'un stock 3 partir de donnees actuelles sur la p4che.

Allelic products of seven isozyme loci were used to identify presumptive hybridization between chinook salmon Oncorhynchus tshawytscha and coho salmon O. kisutch in northern California. First‐generation hybrid salmon (N = 3) were observed in samples from a tributary creek to the Trinity River; from rearing ponds at Camp Creek, a tributary to the Klamath River (N = 14); and from the ocean salmon fishery near Eureka (N = 2). The sample from the Camp Creek rearing ponds consisted of progeny from an inadvertent cross of coho and chinook salmon by hatchery personnel at the Irongate Hatchery. In addition to the artificial production of hybrid salmon at Irongate Hatchery, the alteration of traditional salmon spawning routes by Lewiston Dam on the Trinity River may have lead to natural hybridization between chinook and coho salmon in Deadwood Creek. Accurate quantification of the occurrence of hybridization was impossible due to nonrandom sampling of populations, but we presume to have underestimated the actual hybridization between these two species.