WATER-QUALITY CHANGES AND EFFECTS ON FISH POPULATIONS IN THE HANJIANG RIVER, CHINA, FOLLOWING HYDROELECTRIC DAM CONSTRUCTION

Since its completion in 1973 the Danjiangkou Dam has markedly changed downstream flows, water levels, temperatures, sediment loads and other water quality characteristics in downstream reaches of the Hanjiang River. There have been changes in the growth, spawning behaviour and overwintering condition of local fish populations, in the composition and abundance of food organisms and in the composition of the commercial fish catch. Despite the changed environment and the absence of a fish pass, fish populations are still able to grow and spawn under the new regime. Where conditions are like those of the Hanjiang River, dams may not necessarily have calamitous consequences for fishery production.

Profiling of Complex Microbial Populations by Denaturing Gradient Gel Electrophoresis Analysis of Polymerase Chain Reaction-Amplified Genes Coding for 16S rRNA

We describe a new molecular approach to analyzing the genetic diversity of complex microbial populations. This technique is based on the separation of polymerase chain reaction-amplified fragments of genes coding for 16S rRNA, all the same length, by denaturing gradient gel electrophoresis (DGGE). DGGE analysis of different microbial communities demonstrated the presence of up to 10 distinguishable bands in the separation pattern, which were most likely derived from as many different species constituting these populations, and thereby generated a DGGE profile of the populations. We showed that it is possible to identify constituents which represent only 1% of the total population. With an oligonucleotide probe specific for the V3 region of 16S rRNA of sulfate-reducing bacteria, particular DNA fragments from some of the microbial populations could be identified by hybridization analysis. Analysis of the genomic DNA from a bacterial biofilm grown under aerobic conditions suggests that sulfate-reducing bacteria, despite their anaerobicity, were present in this environment. The results we obtained demonstrate that this technique will contribute to our understanding of the genetic diversity of uncharacterized microbial populations.

Quantitative traits correlative analysis and growth comparison among different populations of bay scallop, Argopecten irradians

The shell traits and weight traits are measured in cultured populations of bay scallop, Argopecten irradians. The results of regression analysis show that the regression relationships for all the traits are significant (P < 0.01). The correlative coefficients between body weight, as well as tissue weight with shell length, shell height and shell width are significant (P < 0.05). But the correlative coefficients between the anterior and posterior auricle length with body weight as well as tissue weight are not significant (P > 0.05). The multiple regression equation is obtained to estimate live body weight and tissue weight. The above traits except anterior and posterior auricle length are used for the growth and production comparison among three cultured populations, Duncan's new multiple range procedure analysis shows that all the traits in the Lingshuiqiao (LSQ) population are much more significant than those of the other two populations (P < 0.01), and there is no significant difference between the Qipanmo (QPM) and Dalijia (DLJ) populations in all traits (P > 0.05). The results indicate that the LSQ population has a higher growth rate and is expected to be more productive than the other two populations.

Studies on hybridization effects of different geographic populations of Chlamys farreri - II. The medium-term growth and development of Chlamys farreri populations from China and Russia and their reciprocal crosses

Based on the research of juvenile (2, 3, 4 months) growth and survival of three populations of two different geographic areas in Chlamys farreri from Russian and China and their F, hybrids derived from Chinese cultural population (CC) female x Russian population (RW) male, Chinese wild population (CW) female x Russian population (RW) male, Russian population (RW) female x Chinese wild population (CW) the study of the medium-term (6, 8, 10, 12 months) growth and development of Chlamys farreri was carried out. The four determined results indicated that there existed different extent heterosis (3% similar to 52 %) for the growth in three types of F-1 hybrids, and the offspring derived from CC female X Rmale had a stronger heterosis among the crosses at the medium-term; the uptrend among traits are wet weight > shell width > shell length > shell height, Chinese cultural population could be recognized as excellent parent, and seasonal variations influence very much on the daily increment and growth rate of each trait of Chlamys farreri and it is only able to survive and could barely grow in winter (6 similar to 8 months), but grows fast in temperate season (10similar to12 months).

Temperature tolerance of young sporophytes from two populations of Laminaria japonica revealed by chlorophyll fluorescence measurements and short-term growth and survival performances in tank culture

The cold-water subtidal brown alga Laminaria japonica has been commercially fanned in the Far East and has been on top of all marine-fanned species in terms of farming area and annual output worldwide. The successful trials of transplantation of young sporophytes from the north to the south in winter along the Chinese coast in the 1950s led to the spreading of cultivation activities down to a latitude of 25-26 degrees N. Up to today, nearly 50% of the annual output of this farmed alga, as a cold-water species, comes from the sub-tropical south in China. The demand to have high-temperature-tolerant strains/ecotypes in farming area calls for a practical method to judge and select the desired parental plants for breeding programs and for seedling production. In this paper, we report our results on using chlorophyll fluorescence measurement and short-term growth performance in tank culture to estimate the temperature tolerance of offspring from two populations, Fujian Farmed Population (FFP) sampled from Fujian province (latitude: 25-26 degrees N) in subtropical area and Qingdao Wild Population (QWP) sampled from Qingdao (latitude: 36 degrees N). Contrary to what has been usually thought, the results revealed that offspring from Qingdao wild population in the north showed better performance both in short-term growth and survival rates and in optimal quantum efficiency (F-v/F-m) when exposed to higher temperature (20-25 degrees C). This result was further confirmed by fluorescence quenching analysis. QWP distributed along the southern distribution limit at a latitude of 36 degrees N in the Pacific west coast is thus taken as a more ideal one than the fanned population in subtropical region as a source of parental plants for breeding high-temperature-tolerant varieties. (c) 2006 Elsevier B.V. All rights reserved.

Inter-simple sequence repeat (ISSR) analysis of genetic variation of Chondrus crispus populations from North Atlantic

ISSR analysis was used to investigate genetic variations of 184 haploid and diploid samples from nine North Atlantic Chondrus crispus Stackhouse populations and one outgroup Yellow Sea Chondrus ocellatus Holmes population. Twenty-two of 50 primers were selected and 163 loci were scored for genetic diversity analysis. Genetic diversity varied among populations, percentage of polymorphic bands (PPB) ranged from 27.0 to 55.8%, H(Nei's genetic diversity) ranged from 0.11 to 0.20 and I(Shannon's information index) ranged from 0.16 to 0.30. Estimators PPB, H and I had similar values in intra-population genetic diversity, regardless of calculation methods. Analysis of molecular variance (AMOVA) apportioned inter-population and intra-population variations for C crispus, showing more genetic variance (56.5%) occurred in intra-population, and 43.5% variation among nine populations. The Mantel test suggested that genetic differentiation between nine C. crispus populations was closely related with geographic distances (R = 0.78, P = 0.002). Results suggest that, on larger distance scale (ca. > 1000 km), ISSR analysis is useful for determining genetic differentiations of C crispus populations including morphologically inseparable haploid and diploid individuals. (c) 2007 Elsevier B.V. All rights reserved.

Loss of allele diversity in introduced populations of the hermaphroditic bay scallop Argopecten irradians

The bay scallop Argopecten irradians is a hermaphroditic bivalve native to the Atlantic coast of the United States that was introduced to China for aquaculture production in 1982. It now supports a major aquaculture industry in China. Introduced species often start with limited genetic variability, which is problematic for the further selective breeding. Bay scallop aquaculture is exclusively hatchery based and as the initial introduction consisted of only 26 scallops, there have been concerns about inbreeding and inbreeding depression in cultured populations in China. In this study, eleven simple sequence repeat (SSR) markers were used to compare genetic variation in cultured populations from China with that in a natural population from the east coast of America. Although the difference in heterozygosity was small, the Chinese populations lost 9 of the 45 alleles (20%) found in the wild population. The reduced allele diversity suggests that the Chinese bay scallop populations experienced a bottleneck in genetic diversity that remains significant despite several recent introductions of new stocks aimed at expanding the gene pool. The loss of allele diversity may affect future efforts in selective breeding and domestication, and results of this study highlight the need for additional introductions, advanced breeding programs that minimize inbreeding and continued genetic monitoring. (c) 2007 Elsevier B.V. All rights reserved.

Genetic structure analysis of natural Sargassum muticum (Fucales, Phaeophyta) populations using RAPD and ISSR markers

Sargassum muticum is important in maintaining the structure and function of littoral ecosystems, and is used in aquaculture and alginate production, however, little is known about its population genetic attributes. In this study, random amplified polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR) markers were used to investigate the genetic structure of four populations of S. muticum and one outgroup of S. fusiforme (Harv.) Setchell from Shandong peninsula of China. The selected 24 RAPD primers and 19 ISSR primers amplified 164 loci and 122 loci, respectively. Estimates of genetic diversity with different indicators (P%, percentage of polymorphic loci; H, the expected heterozygosity; I, Shannon's information index) revealed low or moderate level of genetic variations within each S. muticum population, and a high level of genetic differentiations were determined with pairwise unbiased genetic distance (D) and fixation index (F-ST ) among the populations. The Mantel test showed that two types of matrices of D and F-ST were highly correlated whether from RAPD (r = 0.9706, P = 0.009) or ISSR data (r = 0.9161, P = 0.009). Analysis of molecular variance (AMOVA) was conducted to apportion the variations among and within the S. muticum populations. It indicated that variations among populations were higher than those within populations, being 55.82% verse 44.18% by RAPD and 55.21% verse 44.79% by ISSR, respectively. Furthermore, the Mantel test suggested that genetic differentiations among populations were related to the geographical distances (r > 0.6), namely, conformed to the IBD (isolation by distance) model, as expected from UPGMA (unweighted pair group method with arithmetic averages) cluster analysis. On the whole, the high genetic structuring among the four S. muticum populations along the distant locations was clearly indicated in RAPD and ISSR analyses (r > 0.9, P < 0.05) in our study.

Comparative growth and viability of hybrids between two populations of Chinese shrimp (Fennropenaeus chinensis)

Fenneropenaeus chinensis is confined to the Yellow Sea and Bohai Sea in China and the West Coast of the Korean Peninsula. Intra- and intercross populations were produced between Rushany (YP) and Korean (KN) populations. Seven traits were recorded. The heterosis of hybrids was computed and comparison between treatments was performed by ANOVA. At the fourth month after post-larvae, six indexes of growth trait and viability showed a range of heterosis, ranging from 0.514% to 14.950%. At the fifth month after post-larvae, six indexes of growth trait and viability ranged from -9.000% to 19.090%. The negative heterosis was observed in CL, HST and viability. The heterosis of KN female xYP male tended generally to increase as the age of the Chinese shrimp increased while the heterosis of YP female xKN male tended to decrease. The results indicated that the viability of reciprocal hybrids were not significantly different (P > 0.05) from their parents during the experiment. The result of ANOVA indicated that the F1 hybrids were significantly different (P < 0.05) in WST and TW at the fourth month. The multiple comparisons of LSD test indicated that the hybrids of YP female xKN male were significantly different (P < 0.05) from their parents in TW. The hybrids of YP female xKN male were significantly different (P < 0.05) from the other three combinations in WST. At the fifth months, the F1 hybrids had significant difference (P < 0.05) in body weight while other traits showed no significant differences (P > 0.05) from their parents. The multiple comparisons of LSD test indicated that the hybrids of KN female xYP male were significantly different (P < 0.05) from the KN parents in TW. The results indicate that in experimental conditions, the F-1 hybrids created from two populations of Chinese shrimp showed a certain level of heterosis for growth performance and viability. The crossing scheme may improve growth performance and viability in Chinese shrimp, but the improvement may be limited because effective crossbreeding requires the maintenance of pure, preferably inbred, lines and possibly involves specialized sire and dam lines. Therefore, the exploitation of heterosis through single crossbreeding in Chinese shrimp is of limited utility in practical commercial shrimp aquaculture in spite of the potential of significant heterosis. The crossbreeding of different populations can be applied in the establishment of base populations.