The relationship between fishing methods, fisheries management and the estimation of maximum sustainable yield

The allocation of effort among fishing gears is as important as controlling effort with respect to both sustainable yield and ecosystem management. Differences in age‐specific vulnerability to the fishing method can modify the maximum sustainable yield (MSY) that is obtainable from a fish stock. Different gears or methods are more or less selective for the species targeted, and MSY is rarely, if ever, attainable simultaneously for all species. The different fishing methods capture different types of nontarget species. Some methods will often be more profitable than others, and different user groups will prefer different methods. In many fisheries, it is unlikely that fishing can be limited to a single gear or method, so compromises among them will be required. Global MSY is discussed as a possible reference point for fisheries management. The yellowfin tuna fishery in the eastern Pacific Ocean (EPO) shows all the above characteristics and is used to illustrate effort allocation among fishing methods.     

Impact of biodiversity-climate futures on primary production and metabolism in a model benthic estuarine system

Background

A territory as a prerequisite for breeding limits the maximum number of breeders in a given area, and thus lowers the proportion of breeders if population size increases. However, some territorially breeding animals can have dramatic density fluctuations and little is known about the change from density-dependent processes to density-independence of breeding during a population increase or an outbreak. We suggest that territoriality, breeding suppression and its break-down can be understood with an incomplete-control model, developed for social breeders and social suppression.

Results

We studied density dependence in an arvicoline species, the bank vole, known as a territorial breeder with cyclic and non-cyclic density fluctuations and periodically high densities in different parts of its range. Our long-term data base from 38 experimental populations in large enclosures in boreal grassland confirms that breeding rates are density-regulated at moderate densities, probably by social suppression of subordinate potential breeders. We conducted an experiment, were we doubled and tripled this moderate density under otherwise the same conditions and measured space use, mortality, reproduction and faecal stress hormone levels (FGM) of adult females. We found that mortality did not differ among the densities, but the regulation of the breeding rate broke down: at double and triple densities all females were breeding, while at the low density the breeding rate was regulated as observed before. Spatial overlap among females increased with density, while a minimum territory size was maintained. Mean stress hormone levels were higher in double and triple densities than at moderate density.

Conclusions

At low and moderate densities, breeding suppression by the dominant breeders, But above a density-threshold (similar to a competition point), the dominance of breeders could not be sustained (incomplete control). In our experiment, this point was reached after territories could not shrink any further, while the number of intruders continued to increase with increasing density. Probably suppression becomes too costly for the dominants, and increasing number of other breeders reduces the effectiveness of threats. In wild populations, crossing this threshold would allow for a rapid density increase or population outbreaks, enabling territorial species to escape density-dependency.     

A comparison of anesthetic risk factors and outcomes in light and draft horses

As a result of anatomic and physiologic differences, draft breeds may be at greater risk of developing anesthetic complications. The aim of the study was to evaluate and compare anesthetic management of draft (DR) and light (LT) horses. A case‐matched retrospective study of 371 clinical case records of DR (124 cases) and LT (247 cases) horses presented for general anesthesia between 1991 and 1998 was performed. Data were tabulated and comparisons were made using Student's t‐test (significance p < 0.05). Prior to induction, there were significant differences in mean body weight, rectal temperature, PCV, RBC, and serum TP concentration between DR and LT breeds. There were differences in mean doses of pre‐operative butorphanol (LT 21 µg kg^?1; DR 17 µg kg^?1), induction guaifenesin (LT 99 mg kg^?1; DR 88 mg kg^?1), and intraoperative ketamine (LT 0.35 mg kg^?1; DR 0.56 mg kg^?1) required. There were no significant differences in the mean doses of pre‐operative xylazine, detomidine, or induction barbiturate administered. The mean, average, and maximum concentrations of inspired halothane were significantly higher for DR than for LT horses. Draft horses received 33% less intraoperative IV fluids (8.2 mL kg^?1 hour^?1) than LT horses. Mean anesthetic duration, time to extubation, and standing recovery were not significantly different. Induction complications were not reported for either group. Rates of occurrence of intraoperative bradycardia, hypercarbia, hypoxemia, and metabolic acidosis (SBE, TCO₂, and bicarbonate concentration) did not differ significantly. Average MAP was greater in DR horses, but neither the degree nor the mean duration of hypotension differed between DR and LT horses. Mean PaO₂ was significantly lower in DR (246 mm Hg, 32.8 kPa) than in LT (305 mm Hg, 40.7 kPa) breeds. Draft horses were at greater relative risk of hypoventilation than LT horses. The greater MAP and requirement for halothane and intraoperative ketamine may indicate problems in achieving and maintaining a surgical plane of anesthesia. Draft horses may be at a greater risk of ventilation–perfusion mismatching.     

Predicting the spatio‐temporal distributions of pelagic sharks in the western and central North Pacific

Spatio‐temporal modeling estimates a species distribution function that represents variation in population density over space and time. Recent studies show that the approach may precisely identify spatial hotspots in species distribution, but have not addressed whether seasonal hotspots are identifiable using commonly available fishery data. In this study, we analyzed the seasonal spatio‐temporal distribution of pelagic sharks in the western and central North Pacific using fishery catch rates and a generalized linear mixed model with spatio‐temporal effects. Different spatial distribution patterns were observed between two shark species. The hotspots of shortfin mako (SFM) appeared in the vicinity of the coastal and offshore waters of Japan and the Kuroshio‐Oyashio transition zone (TZ), whereas the hotspots of blue shark (BSH) were widely distributed in the areas from the TZ to the waters of the Emperor Seamount Chain. Shortfin mako distribution changes seasonally with clear north‐south movement, which follows higher sea surface temperatures (SST). However, preferred spring and summer water temperature was still colder than those in fall and winter, but not as cold as for BSH, which did not show seasonal north‐south movement. BSH exhibits seasonal east‐west movement apparently unrelated to temperature. The spatial fishing effort by season generally follows the seasonal movement of temperature possibly making SFM more vulnerable to the fishery than BSH. These findings could be used to reduce the capture risk of bycatch sharks and to better manage the spatial distribution of fishing for targeted sharks.     

Field trials of a formulation containing moxidectin and 6 in 1 vaccines for sheep

Objective: To assess the efficacy and safety of a formulation containing moxidectin and 6 in 1 vaccine in sheep under field conditions.
Design: Efficacy and safety study.
Animals: Two hundred and five crossbred Merino lambs and two hundred and eight Merino ewes were used in the studies.
Procedure: A formulation was made for the simultaneous treatment of sheep with moxidectin and immunisation against clostridial diseases and caseous lymphadenitis. The efficacy against nematodes, vaccine response and safety were assessed.
Results: Effective control of nematodes and responses to antigens were achieved following subcutaneous administration. The formulation was safe to administer; occasional minor tissue reactions were evident, but no other adverse effects of treatment were observed in either pregnant ewes or lambs, using either the recommended dose, or an overdose of the formulation.
Conclusion: Administration of a formulation containing moxidectin, five clostridial antigens and caseous lymphadenitis antigen proved safe and efficacious under field conditions.     

Effects of Interferon‐Tau and Steroids on Cytochrome P450 Activity in Bovine Endometrial Epithelial Cells

The objective of the current study was to examine cyclooxygenase (COX), cytochrome P450 1A (CYP1A) and 2C (CYP2C) activity in bovine endometrial cell cultures following exposure to oxytocin (OT), interferon‐τ (IFN), estradiol (E2) and/or progesterone (P4). Bovine endometrial epithelial cells were treated with OT, IFN, a combination of OT+IFN or control (CON) media for 24 h. For the second experiment, cells were treated with E2, P4, a combination of E2 + P4 or CON media for 24 h. Treatments were performed in triplicate, and the experiment was repeated four times (n = 12 per treatment). Treatment with OT alone increased (p < 0.01) activity of COX compared with CON; however, OT alone did not alter activity of CYP1A (p = 0.55) or CYP2C (p = 0.46) compared with CON. Activity of CYP1A and CYP2C was decreased in cells exposed to IFN (p < 0.01) or OT+IFN (p < 0.01) compared with CON. Treatment with E2 alone did not alter activity of CYP1A (p = 0.64) or CYP2C (p = 0.06) compared with CON. Activity of CYP1A and CYP2C was decreased (p < 0.01) in P4 vs CON. In summary, IFN exposure, irrespective of OT treatment, decreased the activity of CYP1A and CYP2C. Activity of CYP1A was decreased following P4 treatment alone, while that of CYP2C was decreased following both P4 and E2 + P4 treatment. The mixed function monooxygenase enzymes, CYP1A and CYP2C, have been implicated in synthesizing embryotoxic compounds; therefore, downregulation in the endometrium may be necessary during maternal recognition of pregnancy.     

The National Food Consumption Survey (NFCS): South Africa, 1999

OBJECTIVE: The aim of the National Food Consumption Survey (NFCS) in South Africa was to determine the nutrient intakes and anthropometric status of children (1-9 years old), as well as factors that influence their dietary intake. DESIGN: This was a cross-sectional survey of a nationally representative sample of all children aged 1-9 years in South Africa. A nationally representative sample with provincial representation was selected using 1996 Census information. SUBJECTS: Of the 3120 children who were originally sampled data were obtained from 2894, a response rate of 93%. METHODS: The sociodemographic status of each household was assessed by a questionnaire. Dietary intake was assessed by means of a 24-hour recall and a food-frequency questionnaire from the caregivers of the children. Food purchasing practices were determined by means of a food procurement questionnaire. Hunger was assessed by a modified hunger scale questionnaire. Nutritional status was determined by means of anthropometric measurements: height, weight, head circumference and arm circumference. RESULTS: At the national level, stunting (height-for-age below minus two standard deviations (< -2SD) from the reference median) was by far the most common nutritional disorder, affecting nearly one in five children. The children least affected (17%) were those living in urban areas. Even with regard to the latter, however, children living in informal urban areas were more severely affected (20%) compared with those living in formal urban areas (16%). A similar pattern emerged for the prevalence of underweight (weight-for-age < -2SD), with one in 10 children being affected at the national level. Furthermore, one in 10 (13%) and one in four (26%) children aged 1-3 years had an energy intake less than half and less than two-thirds of their daily energy needs, respectively. For South African children as a whole, the intakes of energy, calcium, iron, zinc, selenium, vitamins A, D, C and E, riboflavin, niacin, vitamin B6 and folic acid were below two-thirds of the Recommended Dietary Allowances. At the national level, data from the 24-hour recalls indicated that the most commonly consumed food items were maize, sugar, tea, whole milk and brown bread. For South African children overall, one in two households (52%) experienced hunger, one in four (23%) were at risk of hunger and only one in four households (25%) appeared food-secure. CONCLUSION: The NFCS indicated that a large majority of households were food-insecure and that energy deficit and micronutrient deficiencies were common, resulting in a high prevalence of stunting. These results were used as motivation for the introduction of mandatory fortification in South Africa.