Network analysis suggests changes in food web stability produced by bottom trawl fishery in Patagonia.

Demersal fisheries are one of the top anthropic stressors in marine environments. In the long term, some species are more vulnerable to fishery impacts than others, which can lead to permanent changes on the food web. The trophic relationships between predator and prey constitute the food web and it represents a network of the energy channels in an ecosystem. In turn, the network structure influences ecosystem diversity and stability. The first aim of this study was to describe for the first time the food web of the San Jorge Gulf (Patagonia Argentina) with high resolution, i.e. to the species level when information is available. The San Jorge Gulf was subject to intense fisheries thus our second aim is to analyse the food web structure with and without fishery to evaluate if the bottom-trawl industrial fishery altered the network structure and stability. We used several network metrics like: mean trophic level, omnivory, modularity and quasi-sign stability. We included these metrics because they are related to stability and can be evaluated using predator diets that can weight the links between predators and prey. The network presented 165 species organized in almost five trophic levels. The inclusion of a fishery node adds 69 new trophic links. All weighted and unweighted metrics showed differences between the two networks, reflecting a decrease in stability when fishery was included in the system. Thus, our results suggested a probable change of state of the system. The observed changes in species abundances since the fishery was established, could represent the state change predicted by network analysis. Our results suggests that changes in the stability of food webs can be used to evaluate the impacts of human activity on ecosystems.

Prevalence of chronic pain syndrome in patients who have undergone hallux valgus percutaneous surgery: a comparison of sciatic-femoral and ankle regional ultrasound-guided nerve blocks.

BACKGROUND: Chronic pain syndrome (CPS) is a common complication after operative procedures, and only a few studies have focused on the evaluation of CPS in foot-forefoot surgery and specifically on HV percutaneous correction. The objective of this study was to compare postoperative pain levels and incidence of CPS in two groups of patients having undergone femoral-sciatic nerve block or ankle block regional anaesthesia before hallux valgus (HV) percutaneous surgery and the association between postoperative pain levels and risk factors between these patient groups. METHODS: A consecutive patient series was enrolled and evaluated prospectively at 7 days, 1, 3 and 6 months after surgery. The participants were divided into two groups according to the regional anaesthesia received, femoral-sciatic nerve block or ankle block, and their outcomes were compared. The parameters assessed were postoperative pain at rest and during movement by the numerical rating scale (NRS), patient satisfaction using the Visual Analogue Scale (VAS), quality of life and return to daily activities. Statistical analysis was performed. RESULTS: One hundred fifty-five patients were assessed, 127 females and 28 males. Pain at rest (p < 0.0001) and during movement (p < 0.0001) significantly decreased during the follow-ups; at 6 months, 13 patients suffered from CPS. Over time, satisfaction remained stable (p > 0.05), quality of life significantly increased and patients returned to daily activities and work (p < 0.0001). No significant impact of type of anaesthesia could be detected. ASA 3 (p = 0.043) was associated to higher pain during movement; BMI (p = 0.005) and lumbago (p = 0.004) to lower satisfaction. No operative-anaesthetic complications were recorded. Postoperative pain at rest and during movement improved over time independently of the regional block used, with low incidence of CPS at last follow-up. Among risk factors, only a higher ASA was associated to higher pain during movement, while higher BMI and lumbago to lower satisfaction. CONCLUSIONS: Both ultrasound-guided sciatic-femoral and ankle blocks were safe and effective in reducing postoperative pain with low incidence of CPS at last follow-up. TRIAL REGISTRATION: Clinical Trial NCT02886221 . Registered 1 September 2016.

Does trawl fisheries affect the diet of fishes? A stable isotope analysis approach.

Trawling is the main fishing practice worldwide and its ecosystem effects have been raising concern over the past decades. Long-term impacts can be monitored through changes in the trophic structure, and several studies evaluated trophic level (TL) shifts in fish populations between trawled and untrawled environments. However, published results are contrasting. We performed a metanalysis integrating all available studies that evaluated TL shifts in fishes between trawled and untrawled environments and conducted a local study comparing several features of the trophic ecology in two species of fishes. According to the metanalysis, TL does not change significantly with trawling. In contrast, the local study showed higher TLs and broader isotopic niches in the trawled environment. Diet reconstruction indicated a potential consumption of hake, the main discard component, at the trawled environment. All the studies used in the metanalysis were conducted in the Northern Hemisphere, whereas the local study represents the first data available from the Southern Hemisphere. As industrial commercial fisheries in Argentina are relatively recent, it is possible that our data are capturing the initial stage of ecological changes induced by trawling, compared with the historical fisheries located at the Northern Hemisphere.