摘要:

Concentrations of total mercury were determined for axial muscle tissue of 438 largemouth bassMicropterus salmoidesfrom 46 lakes representing five regions in Connecticut to determine relationships between mercury concentrations and lake characteristics and to assess regional differences in mercury concentrations. Expected concentrations of mercury (EHg) predicted for a length of 356 mm for each population ranged from 0.103 to 0.795 μg/g wet weight. Principal components analysis revealed that, in general, two types of lakes were represented in the data set and were grouped based on hydrologic characteristics. Type-II lakes (artificial impoundments) had a significantly lower mean retention time than type-I lakes (natural drainage lakes) and a significantly larger mean watershed area, watershed area : surface area ratio, watershed area: lake volume ratio, and shoreline development index. MeanEHg was approximately 20% higher in type-II lakes (0.514 μ/g wet weight) than in type-I lakes (0.410 μg/g wet weight;P= 0.08); factors most strongly correlated withEHg differed between lake types. Largemouth bassEHg in type-I lakes was most strongly correlated to particulate phosphorus (r= −0.64) and conductivity (r= −0.55);EHg in type-II lakes was most strongly correlated with retention time (r= 0.76) and watershed area: lake volume ratio (r= −0.75). Stepwise multiple regression revealed that particulate P and mean depth accounted for 51% of the variability inEHg among type-I lakes. Retention time was the only variable retained in stepwise regression of type-II lakes and accounted for 57% of the variation inEHg. Largemouth bassEHg in type-I lakes was significantly different among regions, as were lake variables describing hardness, alkalinity, and productivity.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1998)127<0807:RBCOMI>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Successful cryopreservation of fish spermatozoa has important implications for genomic conservation and for aquaculture. We report the first long-term cryopreservation of ictalurid sperm. Spermatozoa from nine blue catfishIctalurus furcatuswere cryopreserved for 12 months in three concentrations (3.75 × 108, 1.50 × 109, and 6.00 × 109spermatozoa per straw), within two different straw sizes (0.5 and 1.0 mL), and with two cryoprotectants (DMSO or methanol combined with powdered skim milk). Cryopreserved spermatozoa were then used to fertilize lots of 450 eggs of channel catfishIctalurus punctatus.Mean relative fertilization percentage for sperm treated with DMSO was 32% (range of 23–54%) of the fresh control. Spermatozoa frozen with the combination of an intracellular cryoprotectant (methanol) and an extracellular cryoprotectant (skim milk) produced no fertilization. No difference (P> 0.05) was observed between fertilization percentage of spermatozoa frozen in the two straw sizes. The highest level of relative fertilization percentage (54%) was achieved with the highest insemination dose, 6.00 × 109spermatozoa per straw (P< 0.05). There was no difference (P> 0.05) in fertilization percentage between insemination doses of 3.75 × 108and 1.50 × 109spermatozoa per straw. Cryopreservation of blue catfish spermatozoa can be optimized by using the high concentration of sperm (6.00 × 109) and DMSO as cryoprotectant in either 0.5- or 1.0-mL straws.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1998)127<0819:COBCSA>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Random amplified polymorphic DNA (RAPD) analysis was investigated as an alternative to conventional electrophoresis for subspecies identification of largemouth bassMicropterus salmoides.Seventeen primers were analyzed by RAPD for their ability to identify polymorphisms, and the three primers that gave the most polymorphisms were used for the study. Fifteen markers were identified and were shown to indicate fixed differences between the two subspecies. Intergrades of unknown origin were distinguishable from pure Florida and pure northern wild and hatchery stocks, as well as first generation intergrades (F1s). The RAPD analysis was more sensitive than traditional histochemical agarose gel electrophoresis for identification of largemouth bass subspecies.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1998)127<0825:UORAPD>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

We examined allozyme variation in the parents and offspring of 41 crossings of coho salmonOncorhynchus kisutch.Mendelian inheritance previously unreported for Pacific salmon was confirmed at 11 loci:sAAT-4*, sAH*, ALAT*, EST-1*, βGALA*, GAPDH-2*, GPI-B2*, sMDH-A1,2*, PEPA*, PEPC*, andPNP-1*.Independent assortment was found for the following locus pairs:ADA-1*andβGALA*, ALAT*andβGALA*, ALAT*andEST-1*, EST-1*andβGALA*, EST-1*andPEPC*, GAPDH-2*andPNP-1*, βGALA*andGPI-B2*, βGALA*andsMDH-A1,2*, andβGALA*andPEPC*.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1998)127<0833:IOAICS>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Intense fishing for bluefin tunaThunnus thynnusin the western Atlantic Ocean began in the 1960s, when landings peaked at nearly 20,000 metric tons (mt). During the 1970s, landings averaged about 5,000 mt. The International Commission for the Conservation of Atlantic Tunas (ICCAT) established a total allowable catch (TAC) of 1,160 mt in 1982 and has set limits ranging from 1,995 to 2,660 mt annually since. The Commission's assessments indicate that unrestricted fishing through the 1960s and 1970s resulted in a sharp decline in abundance, primarily because heavy fishing on young fish wasted potentially good recruitment. Since the late 1980s, ICCAT management has stabilized the western Atlantic population, and recently there are signs of improvement. Resource assessments and management of western Atlantic bluefin tuna are subjects of severe controversy. Two of the most controversial issues are the stock assessment implications of fish migrations between the western and eastern Atlantic management units and the strategies for rebuilding abundance in the western Atlantic. In 1994, the U.S. National Research Council (NRC) was commissioned to review bluefin tuna stock assessments with particular emphasis on the issue of population mixing. The NRC report was widely misinterpreted as being more optimistic than it really was for the western population. Analyses by the NRC committee indicated that the abundance of spawning age fish in the west was higher than the value estimated in the 1993 ICCAT assessment but also that recruitment in the western Atlantic had failed so badly that some year-classes were estimated to have zero fish. Projections of future population size based on the NRC analyses indicated that recent levels of catch could not have been sustained. The critical issue now facing fishery managers is how to rebuild the population to a size, estimated to be about eight times the current size, that can produce maximum sustainable yield. One strategy (referred to as “active”) is to reduce the fishing mortality, which would permit some immediate rebuilding and enhance the likelihood of better recruitment in the future. Another strategy (referred to as “passive”) is to wait for natural variability in recruitment to bring a fortuitously strong year-class that would be invested in rebuilding, rather than in harvest. The most recent ICCAT assessment evaluated rebuilding strategies, but the method used has limitations that should be understood before decisions about rebuilding are made.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1998)127<0838:ACOWAB>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0002-8487    

DOI:10.1577/1548-8659(1998)127<0856:ARM>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0002-8487    

DOI:10.1577/1548-8659(1998)127<0857:MSOF>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor