[Demographic analysis of the blue shark, Prionace glauca, in the North Atlantic Ocean].

The blue shark, Prionace glauca, is the main by-catch species in tuna longline fishery. As one of top species in the oceanic food webs, the blue shark plays an important role in the marine ecosystem. Traditional stock assessment methods are difficult to accurately evaluate the population dynamic for this shark because of limited data. Based on life-history parameters of the blue shark in the North Atlantic, demographic analysis was employed to estimate the demographic parameters and evaluate the potential exploitation for the blue shark. Moreover, we discussed the relationship between age at first capture and critical value of fishing mortality corresponding to the value of intrinsic rate of natural increase 0. The results showed that the survival rate (S) of blue shark from 0.719 to 0.820, intrinsic rate of natural increase (r0) from 0.250 to 0.381, time of population doubling (tx2) from 1.819 to 2.773 years, reproduction rate per generation (R0) from 6.600 to 22.255, and generation time (G) from 8.498 to 10.162 years. The sensitivity analysis for the life history parameters revealed that the uncertainties of natural mortality existed in the first age class, age at maturity and maximum age had slight influence on the demographic parameters. Fishing mortality (Fc) increased with the age at first capture. When the age at first capture (tc) was more than five, there was no obvious relationship between Fc and tc.

[Vertical distribution of main species captured by tuna longline fishery in the southeast Pacific Ocean].

Information of vertical distribution of longline-hook species is important for the development of effective measures to mitigate bycatch, and very helpful for better understanding of the oceanic ecosystem structure and implementation of ecosystem-based fisheries management. Based on depth data of longline hook and capture hook position of pelagic species, collected by on board scientific observer in the southeast Pacific Ocean from September 2013 to January 2014, shoaling rate of longline hook and vertical distribution of 14 pelagic species were analyzed. The results showed that the relative shoaling rate range of longline hook was 8.9% - 17.1%, and the average relative shoaling rate was 13.5%. The depth ranges of 14 capture species were different. The species with the deepest depth was Opah (Lampris guttatus), and the species with the shallowest depth was skipjack (Katsuwonus pelamis). Except for yellowfin tuna (Thunnus albacares) and striped marlin (Tetrapturus audax), the mean depth and depth distributions of bycatch species were significantly different from that of the targeted albacore tuna (Thunnus alalunga).

Development of an ERIC sequence typing scheme for Laribacter hongkongensis, an emerging pathogen associated with community-acquired gastroenteritis and travellers' diarrhoea.

Laribacter hongkongensis is a potential emerging pathogen, associated with community-acquired diarrhoea. For epidemiological purposes, different molecular typing methods, such as pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing, have been developed for this pathogen. However, these methods require specialized equipment and costly reagents. More importantly, they are labour-intensive and time-consuming, which is not really suitable for foodborne disease outbreak investigations. In this study, we developed a rapid and reliable method using 22-mer primers specific for the enterobacterial repetitive intergenic consensus sequence (ERIC). PFGE was used for comparison, to evaluate this method. A total of 81 isolates of L. hongkongensis were examined: 79 isolates recovered from food of diverse origins and two strains derived from patients with L. hongkongensis-associated infection. Typing patterns and clustering analysis indicated that the 81 L. hongkongensis isolates were grouped into 21 and 13 genotypes by ERIC-PCR and PFGE, respectively. ERIC-PCR was found as reproducible as PFGE. A high percentage (70.4%) of isolates yielded distinguishable ERIC-PCR patterns, which were concordant with the results from PFGE. These results suggest that ERIC-PCR is valuable for use in the epidemiological investigation of L. hongkongensis.

[Prevalence and antimicrobial susceptibility of Laribacter hongkongensis and enterotoxigenic Escherichia coli isolated from patients with diarrhea in Guangzhou].

OBJECTIVE: To survey the prevalence of enterotoxigenic Escherichia coli (ETEC) and Laribacter hongkongensis (LH) and their drug resistance in diarrhea patients in Guangzhou. METHODS: We detected 646 fecal cases collected between Sep 2008 and Oct 2009 from the out-patient and emergency departments in a hospital. EC enriched culture medium was used for enrichment. MAC- and CMAC-specific culture media were used to isolate ETEC and LH from the specimens. The biochemical agents API20NE and API20E were employed for biochemical identification, and PCR was used for genetic identification. K-B disk diffusion method was used for antimicrobial susceptibility testing. RESULTS: No LH was detected in the total 646 patients, and 38 patients were positive for ETEC, with a detection rate of 6%. Antibiotics resistance test showed that 38 strains of ETEC had a high resistance rate to penicillin, tetracycline and sulfa, but remained sensitive to cephalosporins. CONCLUSIONS: LH may have a low prevalence in Guangzhou. The incidence of diarrhea caused by ETEC tends to decrease as compared with that a decade ago, and further multi-center survey is needed for confirmation. Consumption of aquatic products may be one of the major risk factors for ETEC infection. Cephalosporins can be used for ETEC-induced diarrhea.