Recovery and status of shortnose sturgeon in the Hudson River

Shortnose sturgeon (Acipenser brevirostrum), an endangered species, has experienced a several-fold increase in abundance in the Hudson River in recent decades. This population growth followed a substantial improvement in water quality during the 1970s to a large portion (c. 40%) of the species' summertime nursery area. Age structure and growth were investigated to evaluate the hypothesis that improvements in water quality stimulated population recovery through increased survival of young of the year juveniles. Specimens were captured using gill nets bi-monthly from November 2003 to November 2004 (n = 596). Annuli in fin spine sections were used to generate estimates of sturgeon age. Based upon a marginal increment analysis, annuli were determined to form at an annual rate. Age determinations yielded a catch composed of age 5-30 years for sizes 49-105cm Total Length (n = 554). Individual growth rate (von Bertalanffy coefficients: TL, = 1045mm, K = 0.07) for the population was similar to previous growth estimates within the Hudson River as well as proximal estuaries. Hindcast year-class strengths, based upon a recent stock assessment (Bain et al. 2000) and corrected for gill net mesh selectivity and cumulative mortality indicated high recruitments (28,000-43,000 yearlings)during 1986-1992, which were preceded and succeeded by c.5-year periods of lower recruitment (5,000-1 5,000 yearlings). Recruitment patterns were corroborated by trends in shortnose sturgeon bycatch from a Hudson utilities-sponsored monitoring program. Results indicated that Hudson River shortnose sturgeon abundance increased due to the formation of several strong year-classes occurring about five years subsequent to improved water quality in important nursery and forage habitats in the upper Hudson River estuary. (PDF contains 108 pages.)

Effects of a large fishing closure on benthic communities in the western Gulf of Maine: recovery from the effects of gillnets and otter trawls

The recovery of benthic communities inside the western Gulf of Maine fishing closure area was evaluated by comparing invertebrate assemblages at sites inside and outside of the closure four to six years after the closure was established. The major restriction imposed by the closure was a year-round prohibition of bottom gillnets and otter trawls. A total of 163 seafloor sites (~half inside and half outside the closure) within a 515-km2 study area were sampled with some combination of Shipek grab, Wildco box corer, or underwater video. Bottom types ranged from mud (silt and clay) to boulders, and the effects of the closure on univariate measures (total density, biomass, taxonomic richness) of benthos varied widely among sediment types. For sites with predominantly mud sediments, there were mixed effects on inside and outside infauna and no effect on epifauna. For sites with mainly sand sediments, there were higher density, biomass, and taxonomic richness for infauna inside the closure, but no significant effects on epifauna. For sites dominated by gravel (which included boulders in some areas), there were no effects on infauna but strong effects on epifaunal density and taxonomic richness. For fishing gear, the data indicated that infauna recovered in sand from the impacts of otter trawls operated inside the closure but that they did not recover in mud, and that epifauna recovered on gravel bottoms from the impact of gillnets used inside the closure. The magnitudes of impact and recovery, however, cannot be inferred directly from our data because of a confounding factor of different fishing intensities outside the closure for a direct comparison of preclosure and postclosure data. The overall negative impact of trawls is likely underestimated by our data, whereas the negative impact of gillnets is likely overestimated.

Evolutionary associations between sand seatrout (Cynoscion arenarius) and silver seatrout (C. nothus) inferred from morphological characters, mitochondrial DNA, and microsatellite markers

The evolutionary associations between closely related fish species, both contemporary and historical, are frequently assessed by using molecular markers, such as microsatellites. Here, the presence and variability of microsatellite loci in two closely related species of marine fishes, sand seatrout (Cynoscion arenarius) and silver seatrout (C. nothus), are explored by using heterologous primers from red drum (Sciaenops ocellatus). Data from these loci are used in conjunction with morphological characters and mitochondrial DNA haplotypes to explore the extent of genetic exchange between species offshore of Galveston Bay, TX. Despite seasonal overlap in distribution, low genetic divergence at microsatellite loci, and similar life history parameters of C. arenarius and C. nothus, all three data sets indicated that hybridization between these species does not occur or occurs only rarely and that historical admixture in Galveston Bay after divergence between these species was unlikely. These results shed light upon the evolutionary history of these fishes and highlight the genetic properties of each species that are influenced by their life history and ecology.

Spatial and seasonal abundance of sand seatrout (Cynoscion arenarius) and silver seatrout (C. nothus) off the coast of Texas, determined with twenty years of data (1987–200

Sand seatrout (Cynoscion arenarius) and silver seatrout (C. nothus) are both found within the immediate offshore areas of the Gulf of Mexico, especially around Texas; however information is limited on how much distributional overlap really occurs between these species. In order to investigate spatial and seasonal differences between species, we analyzed twenty years of bay and offshore trawl data collected by biologists of the Coastal Fisheries Division, Texas Parks and Wildlife Department. Sand seatrout and silver seatrout were distributed differently among offshore sampling areas, and salinity and water depth appeared to correlate with their distribution. Additionally, within the northernmost sampling area of the gulf waters, water depth correlated significantly with the presence of silver seatrout, which were found at deeper depths than sand seatrout. There was also an overall significant decrease in silver seatrout abundance during the summer season, when temperatures were at their highest, and this decrease may have indicated a migration farther offshore. Sand seatrout abundance had an inverse relationship with salinity and water depth offshore. In addition, sand seatrout abundance was highest in bays with direct passes to the gulf and correlated with corresponding abundance in offshore areas. These data highlight the seasonal and spatial differences in abundance between sand and silver seatrout and relate these differences to the hydrological and geological features found along the Texas coastline.

Monoculture of silver barb (Puntius gonionotus Bleeker) in rice floodwaters in Bangladesh

On-station and on-farm trials with silver barb (Puntius gonionotus) monoculture in rice floodwaters in Bangladesh are summarized and discussed in this article.

Mono- and polyculture of silver barb (Puntius gonionotus) in deepwater rice systems in Bangladesh

Experiments with fish enclosures were conducted at the Deepwater Rice Farming Systems Research Site at Shuvullah, Mirzapur, Bangladesh. The objective was to study the performance of silver barb (Puntius gonionotus) called Thai sharputi or rajputi in Bangladesh in mono-and-polyculture with grass carp (Ctenopharyngodon idella), common carp (Cyprinus carpio), catla (Catla catla) and rohu (Labeo rohita). Each enclosure measured 21 m x 21 m with an approximate net height of 3.5 m. The stocking densities per cubic meter were 1 fingerling for Thai sharputi monoculture (enclosure 1), and 2 fingerlings for the polyculture systems (enclosure 2 and 3). The species ratio for enclosure 2 was 0.37:0.27:0.02:0.34 (grass carp:Thai sharputi:common carp:catla) and for enclosure 3, 0.4:0.4:0.2 (catla:rohu:Thai sharputi). In monoculture (enclosure 1), Thai sharputi performed well. This relatively good production was mainly attributed to the use of appropriately sized fingerlings and rapid growth from consumption of an abundant supply of azolla in addition to feed given. For the polyculture in enclosure 2, the average weight gain of common carp was the highest (673 g) followed by grass carp (475 g) and Thai sharputi (286 g). For the polyculture in enclosure 3, the length and weight gains for Thai sharputi were almost the same as for the monoculture.

Preliminary results of a silver carp breeding program in Vietnam

The article describes the silver carp (Hypophthalmichthys harmandi and Hypophthalmichthys molitrix) breeding program in Vietnam.

Overview of Mark-recovery Studies on Adult and Juvenile Atlantic Menhaden, Brevoortia tyrannus, and Gulf Menhaden, B. patronus

Extensive mark-recapture studies using internal ferromagnetic tags have been conducted on Atlantic menhaden, Brevoortia tyrannus, and Gulf menhaden, B. patronus. From 1966 through 1969, 1,066,357 adult Atlantic menhaden were tagged; subsequently, from 1970 through 1987, 428,272 juveniles of this species were tagged. Similarly, from 1969 through 1971, 75,673 adult Gulf menhaden were tagged; concurrently from 1970 through 1985, 236,936 juveniles were tagged and released. This report provides an overview of the history of the tagging program, methodologies for both release and recovery activities, a summary of release areas and number of fish tagged within each area, and a review of assumptions necessary for the analysis of this type of mark-recovery data. The resulting data sets have proven to be highly useful for a variety of analyses ranging from determination of migratory patterns and population structure to estimating mortality rates. The relatively wide range of acceptance of tagging results by laymen, industry, and analysts alike have made these data extremely useful for management-oriented analyses.

Survey of the lesser silver water beetle Hydrochara caraboides in Cheshire

This is the report on the Survey of the Lesser Silver Water Beetle Hydrochara caraboides in Cheshire 1997 by the English Nature Research Reports. The three surveyed areas were the ponds at Reaseheath, Mickle Trafford and Brookhouse Farm. The report goes through the method of survey and individual results for each location/pond, aspects of the breeding sites considered favourable to Hydrochara caraboides as depth, vegetation, predators and prey species, surrounding land. It comes with suggestions for further work and appendixes. Appendix A contains tabulated lists of plants and invertebrates found in the various ponds, Appendix B shows grid references and a brief description of ponds at Brookhouse Farm, pond diagrams are plotted in Appendix C.