Limited genetic structure of Gulf Menhaden (Brevoortia patronus), as revealed by microsatellite markers developed for the genus Brevoortia (Clupeidae)

Long-term sustainable management of wild populations should be based on management actions that account for the genetic structure among populations. Knowledge of genetic structure and of the degree of demographic exchange between discreet [sic] populations allows managers to better define management units. However, adequate gene loci for population assessments are not always available. In this study, variable co-dominant DNA loci in the heavily exploited marine genus Brevoortia were developed with a microsatellite-enriched DNA library for the Gulf Menhaden (Brevoortia patronus). Microsatellite marker discovery was followed by genetic characterization of 4 endemic North American Brevoortia species, by using 14 novel loci as well as 5 previously described loci. Power analysis of these loci for use in species identification and genetic stock structure was used to assess their potential to improve the stock definition in the menhaden fishery of the Gulf of Mexico. These loci could be used to reliably identify menhaden species in the Gulf of Mexico with an estimated error rate of α=0.0001. Similarly, a power analysis completed on the basis of observed allele frequencies in Gulf Menhaden indicated that these markers can be used to detect very small levels of genetic divergence (Fst≈0.004) among simulated populations, with sample sizes as small as n=50 individuals. A cursory analysis of genetic structure among Gulf Menhaden sampled throughout the Gulf of Mexico indicated limited genetic structure among sampling locations, although the available sampling did not reach the target number (n=50) necessary to detect minimal values of significant structure.

Reproduction and recruitment of white mullet (Mugil curema) to a tropical lagoon (Margarita Island, Venezuela) as revealed by otolith microstructure

The reproductive activity and recruitment of white mullet (Mugil curema) was determined by observations of gonad development and coastal juvenile abundance from March 1992 to July 1993. Adults were collected from commercial catches at three sites in northeastern Venezuelan waters. Spawning time was determined from the observation of macroscopic gonadal stages. Coastal recruitment was determined from fish samples collected biweekly by seining in La Restinga Lagoon, Margarita Island, Venezuela. The examination of daily growth rings on the otoliths of coastal recruits was used to determine their birth date and estimate the period of successful spawning. Fish with mature gonads were present throughout the year but were less frequent between September and January when spawning individuals migrated offshore. In both years, juvenile recruitment to the lagoon was highest between March and June when high densities of 25–35 mm juveniles were observed. Back-calculated hatching-date frequency distributions revealed maximum levels of successful spawning in December–January that were significantly correlated with periods of enhanced upwelling. The relation between the timing of successful spawning and the intensity of coastal recruitment in white mullet was likely due to variations in food availability for first-feeding larvae as well as to variations in the duration of the transport of larvae shoreward as a result of varying current conditions associated with upwelling.

Population structure of king mackerel (Scomberomorus cavalla) around peninsular Florida, as revealed by microsatellite DNA

A total of 1006 king mackerel (Scomberomorus cavalla) representing 20 discrete samples collected between 1996 and 1998 along the east (Atlantic) and west (Gulf) coasts of Florida and the Florida Keys were assayed for allelic variation at seven nuclear-encoded microsatellites. No significant deviations from Hardy-Weinberg equilibrium expectations were found for six of the microsatellites, and genotypes at all microsatellites were independent. Allele distributions at each microsatellite were independent of sex and age of individuals. Homogeneity tests of spatial distributions of alleles at the microsatellites revealed two weakly divergent “genetic” subpopulations or stocks of king mackerel in Florida waters—one along the Atlantic coast and one along the Gulf coast. Homogeneity tests of allele distributions when samples were pooled along seasonal (temporal) boundaries, consistent with the temporal boundaries used currently for stock assessment and allocation of the king mackerel resource, were nonsignificant. The degree of genetic divergence between the two “genetic” stocks was small: on average, only 0.19% of the total genetic variance across all samples assayed occurred between the two regions. Cluster analysis, assignment tests, and spatial autocorrelation analysis did not generate patterns that were consistent with either geographic or spatial-temporal boundaries. King mackerel sampled from the Florida Keys could not be assigned unequivocally to either “genetic” stock. The genetic data were not consistent with current spatial-temporal boundaries employed in stock assessment and allocation of the king mackerel resource. The genetic differences between king mackerel in the Atlantic versus those in the Gulf most likely stem from reduced gene flow (migration) between the Atlantic and Gulf in relation to gene flow (migration) along the Atlantic and Gulf coasts of peninsular Florida. This difference is consistent with findings for other marine fishes where data indicate that the southern Florida peninsula serves (or has served) as a biogeographic boundary.

Consumption pattern and consumer preference for value-added fish and fish products in north zone of India

Present paper attempts to analyze consumption pattern and consumer preferences towards value-added fish and fish products in north zone of India. Results reveal that socio economic variables affect consumption of value-added fish and fish products. A total of 49 percent respondents were of middle age group (35 to 50 years). All were literates except 7% from the rural area. All were purchasing fish at least once in 15 days. A total of 90% respondents in rural, 11% in semi urban and 50% in urban area were unaware of value-added fish and fish products. About 10% of respondents had consumed it, out of which most were from urban area. Demand analysis by Cobb Douglas (CD) Demand function revealed that when price of fish, price of the substitutes, income of family and family size were used as independent variables, variation in demand of fish explained by CD Demand function was about 39% in urban area, 24% in semi urban area and 22% in rural area. From Garette ranking technique major problems in fish consumption found were irregular supply, lack of fresh fish, high price and presence of bones in fish. While lack of awareness, unavailability, no preference and unacceptable taste were major problems for consumption of value-added fish and fish products.