Effects of cryptic mortality and the hidden costs of using length limits in fishery management

Fishery collapses cause substantial economic and ecological harm, but common management actions often fail to prevent overfishing. Minimum length limits are perhaps the most common fishing regulation used in both commercial and recreational fisheries, but their conservation benefits can be influenced by discard mortality of fish caught and released below the legal length. We constructed a computer model to evaluate how discard mortality could influence the conservation utility of minimum length regulations. We evaluated policy performance across two disparate fish life‐history types: short‐lived high‐productivity (SLHP) and long‐lived low‐productivity (LLLP) species. For the life‐history types, fishing mortality rates and minimum length limits that we examined, length limits alone generally failed to achieve sustainability when discard mortality rate exceeded about 0.2 for SLHP species and 0.05 for LLLP species. At these levels of discard mortality, reductions in overall fishing mortality (e.g. lower fishing effort) were required to prevent recruitment overfishing if fishing mortality was high. Similarly, relatively low discard mortality rates (>0.05) rendered maximum yield unobtainable and caused a substantial shift in the shape of the yield response surfaces. An analysis of fishery efficiency showed that length limits caused the simulated fisheries to be much less efficient, potentially exposing the target species and ecosystem to increased negative effects of the fishing process. Our findings suggest that for overexploited fisheries with moderate‐to‐high discard mortality rates, reductions in fishing mortality will be required to meet management goals. Resource managers should carefully consider impacts of cryptic mortality sources (e.g. discard mortality) on fishery sustainability, especially in recreational fisheries where release rates are high and effort is increasing in many areas of the world.     

Investigation on redox status and gene expression related to larval cryopreservation in the Pacific oyster Crassostrea gigas

This study evaluated the effects of larval cryopreservation on redox status of post-thaw trochophore larvae and on gene expression in post-thaw trochophore larvae, D-larvae, umbo larvae, eyed larvae and spat, with the aim to understand the effects of cryodamage in the Pacific oyster Crassostrea gigas. The results showed that total antioxidant capacity was significantly higher in the cryopreserved larvae than in the control group (P?<?0.05), with no significant difference in the production of reactive oxygen species between these two groups (P?>?0.05). The expressions of FADD, Bax1, Baxlike, Bcl2, CASP7 and CAT were significantly downregulated in post-thaw trochophore larvae, whereas the expression of the SOD gene was significantly upregulated. However, the expressions of all of these genes did not significantly differ at later developmental stages. In the cryopreserved group, the expressions of GPX and ATG6 were downregulated in trochophore larvae and upregulated in D-larvae, while there were no signficant changes in the expressions of BI-1, Caspase 3 and ATG8 at all developmental stages investigated. Taken together, these results suggest that the larval cryopreservation technique developed for the Pacific oyster may compromise the survival of post-thaw trochophore larvae by modifying the redox status and gene expression patterns, but that they have limited effects, if any effect at all, after the umbo stage, indicating that the umbo stage should be used for assessing post-thaw larval performance in this species.

     

Robust two-stage approach to repeated measurements analysis of chronic ozone exposure in rats

A robust two-stage approach is used to reanalyze the repeated measurements from an experiment of airway responsiveness in rats randomized to long-term exposure at four ozone doses. The concentration-response data generated for each rat may be represented as a hierarchical nonlinear model encompasing the sources of variation within and between individual profile for each rat, the conditional modeling approach can assess the adequacy of an assumed mean model, a fundamental advantage not intrinsic to marginal techniques. The two-stage population inference is based on the estimated individual parameters, thus maintaining an intuitive appeal to the toxicologists who traditionally have fitted a separate curve for each animal and then applied ANOVA to the summary statistics. However, we formally adjust the standard errors for the extra variability due to the initial estimation of the individual parameters and also allow for their within-rat correlation. The robust two-stage method appropriately down weights the a berrant responses arising sporadically within individualsand, more importantly, the rats which may be outlying relative to the usual population variation. The true effect of chronic ozone exposure, including a significant gender interaction, may be masked by a few rats which exert undue influence on the population estimates in a nonrobust analysis.     

Cretaceous drowning of reefs on mid-pacific and Japanese guyots

Reefs dredged on guyots of the Mid-Pacific Mountains and the Japanese Seamounts yield middle Cretaceous fossils, indicating that submergence killed off the fauna of the reefs sometime during the Albian-Cenomanian. Eustatic rise of sea level is probably responsible.     

Helicobacter spp. from gastric biopsies of stranded South American fur seals (Arctocephalus australis)

Gastrointestinal lesions with uncertain etiology have been widely described among pinnipeds. The aim of our study was to investigate the presence of Helicobacter spp. in the gastric mucosa of South American fur seals (Arctocephalusaustralis). Gastric biopsies from thirteen seals, stranded on the shores of the Southwestern Atlantic Ocean in Argentina, were evaluated for the presence of Helicobacter spp. by PCR and DNA sequence analysis. Six gastric biopsies were positive for Helicobacter spp. Pairwise sequence comparisons showed less than 95% identity to novel Helicobacter spp. described from pinnipeds from North America and Australia. However, phylogenetic analysis revealed that the South American fur seal sequences clustered with 99-100% homology with H. cetorum, a species isolated from dolphins and whales. The presence of H. cetorum in pinnipeds, if confirmed by its isolation from the gastric mucosa of these mammals, demonstrates the wide host range of this bacterium in the marine environment.     

A survey on canine leishmaniasis and phlebotomine sand flies in central Italy

Zoonotic visceral leishmaniasis (ZVL) is a vector-transmitted zoonosis caused by the parasitic protozoan Leishmania infantum. Bloodsucking sand flies of the subfamily Phlebotominae are the obligatory insect hosts, and the dog is the only domestic reservoir.This study reports data from a survey of canine infection and sand fly phlebotomine monitoring in the province of Perugia in central Italy. The overall seroprevalence in a total of 100 dogs tested was 8% (95% confidence interval: 3.8-15.6%). Data analysis revealed that serological positivity was statistically associated with age (p-value = 0.03) and the area where dogs lived. Standard blacklight traps employed for sampling Culicoides midges in bluetongue disease surveillance were used in phlebotomine monitoring. A total of 5698 sand flies were collected and the two species, Leishmania competent vectors, were identified, Phlebotomus perfiliewi (50%) and Phlebotomus perniciosus (30%).     

A melanocortin 1 receptor allele suggests varying pigmentation among Neanderthals

The melanocortin 1 receptor (MC1R) regulates pigmentation in humans and other vertebrates. Variants of MC1R with reduced function are associated with pale skin color and red hair in humans of primarily European origin. We amplified and sequenced a fragment of the MC1R gene (mc1r) from two Neanderthal remains. Both specimens have a mutation that was not found in approximately 3700 modern humans analyzed. Functional analyses show that this variant reduces MC1R activity to a level that alters hair and/or skin pigmentation in humans. The impaired activity of this variant suggests that Neanderthals varied in pigmentation levels, potentially on the scale observed in modern humans. Our data suggest that inactive MC1R variants evolved independently in both modern humans and Neanderthals.     

Genital herpesvirus hominis type 2 infection: an experimental model in cebus monkeys

Genital infection with herpesvirus hominis type 2 was established in ten female cebus monkeys. Clinical and laboratory findings in the cebus mimic closely those observed in humans, thus providing an experimental model which may be used in the study of the possible role of genital herpetic infection in cervical cancer and in perinatal and chronic neurological diseases.     

Two latent variable risk assessment approaches for mixed continuous and discrete outcomes from developmental toxicity data

Measurements of both continuous and discrete outcomes are encountered in many statistical problems. Here we consider the particular context of teratology studies, where quantitative risk asessment is aimed at determining the effect of dose on the probability that an individual fetus is malformed or of low birth weight, both being important measures of teratogenicity. We will introduce two different joint marginal mean models for outcomes of a mixed nature. First, we propose the Plackett-Dale approach, where for each binary outcome it is assumed that there exists an underlying glatent variable. The latent malformation outcomes are then assumed to follow a Plackett distribution. The second approach we consider is a probit approach. Here it is assumed that there exists an underlying continuous variable for each binary outcome, so the joint distribution for weight and malformation can be assumed to follow a multivariate normal distribution. In both cases, specification of the full distribution will be avoided using pseudolikelihood and generalized estimating equations methodology, respectively. Quantitative risk assessment is illustrated using data from two developmental toxicology experiments.     

Predicting early life connectivity of Antarctic silverfish,an important forage species along the Antarctic Peninsula

The early life stages of the Antarctic silverfish (Pleuragramma antarctica), an important prey species for higher predators in the Southern Ocean ecosystem, dominate the larval fish assemblages of the Bransfield Strait, one of the most important areas for larval retention off the Antarctic Peninsula. Nevertheless, the spatial location of areas where they were spawned and the timing of larval hatching remain unknown. By linking Lagrangian particle tracking simulations with age data obtained using otolith microincrements from fish caught north of Joinville Island in a pelagic survey, we estimated the distribution of hatch dates and subsequent growth rates of silverfish reaching the Bransfield Strait, and predicted the areas where they were spawned. Larval hatching peaked during the last week of December, and the inner shelf and shelf break, east of the Larsen Ice shelf, were the dominant areas predicted to contribute to larval assemblages in the Bransfield Strait. Over simulated periods of 600–630 days, 35–40% of particles remained within the Bransfield Strait, suggesting an important source of supply to higher predators feeding off the northern Antarctic Peninsula. The daily growth rate at the mean size of 22.3 mm was 0.18 mm, corresponding to a daily change in size of approximately 0.82% standard length (SL), and large variability in growth rate suggested a wide range of environmental conditions experienced during the period of advection from the spawning areas. These results provide spatial predictions that can be tested empirically in future studies, using the simulated trajectories to inform sampling design and spatial coverage.