Importance of the relative levels of dietary arachidonic acid and eicosapentaenoic acid for culture performance of gilthead seabream (Sparus aurata) larvae

The effect of different arachidonic acid (ARA) dietary contents at several dietary eicosapentaenoic acid (EPA) levels on the growth, survival and biochemical composition of gilthead seabream larvae was studied to better define the importance of this fatty acid as a function of EPA. Larvae of 18 days were fed one of the five isonitrogenous and isolipidic microdiets with three different EPA (0.3%, 2% and 4%) and ARA amounts (0.1%, 0.6% and 1.2%). Although a dietary increase in either ARA or EPA alone did not improve survival significantly, the increase in both fatty acids significantly enhanced growth and survival, suggesting an optimum dietary value of EPA:ARA close to 4:1.2. Dietary ARA was more efficiently incorporated into larval tissues than EPA. Increased dietary EPA or ARA contents reduced the incorporation of ARA or EPA into larval lipids, indicating their competition as substrates for different enzymes. The possible negative effect of further elevation of dietary ARA and its competition with EPA for phospholipids synthesis deserves further studies in marine fish larvae.     

Strong fisheries management and governance positively impact ecosystem status

Fisheries have had major negative impacts on marine ecosystems, and effective fisheries management and governance are needed to achieve sustainable fisheries, biodiversity conservation goals and thus good ecosystem status. To date, the IndiSeas programme (Indicators for the Seas) has focussed on assessing the ecological impacts of fishing at the ecosystem scale using ecological indicators. Here, we explore fisheries ‘Management Effectiveness’ and ‘Governance Quality’ and relate this to ecosystem health and status. We developed a dedicated expert survey, focused at the ecosystem level, with a series of questions addressing aspects of management and governance, from an ecosystem‐based perspective, using objective and evidence‐based criteria. The survey was completed by ecosystem experts (managers and scientists) and results analysed using ranking and multivariate methods. Results were further examined for selected ecosystems, using expert knowledge, to explore the overall findings in greater depth. Higher scores for ‘Management Effectiveness’ and ‘Governance Quality’ were significantly and positively related to ecosystems with better ecological status. Key factors that point to success in delivering fisheries and conservation objectives were as follows: the use of reference points for management, frequent review of stock assessments, whether Illegal, Unreported and Unregulated (IUU) catches were being accounted for and addressed, and the inclusion of stakeholders. Additionally, we found that the implementation of a long‐term management plan, including economic and social dimensions of fisheries in exploited ecosystems, was a key factor in successful, sustainable fisheries management. Our results support the thesis that good ecosystem‐based management and governance, sustainable fisheries and healthy ecosystems go together.     

Predation by the polyclad flatworm Imogine mediterranea on the cultivated mussel Mytilus galloprovincialis in Bizerta Lagoon (northern Tunisia)

This study was carried out to investigate a paradigm of predation under natural conditions in Bizerta lagoon. The free‐living marine polyclad flatworm Imogine mediterranea was found to feed on the commercial mussel Mytilus galloprovincialis. Such predation could represent a real threat to mytiliculture at this site. Our field experiments have shown that the mortality of the commercial mussel as a result of active predation by this polyclad is approximately 52% when one polyclad and one prey were placed together in a same experimental container. We found a statistically significant relationship between the size of the polyclad and the extent to which the mussels were disabled or completely eaten. Moreover, in our field experiments, the times required for predation‐caused decreases of populations of the bivalves, that is, LT₁₀, LT₂₅ and LT₅₀, decreased significantly with increases in the size of the polyclad. The time, LT₅₀, required for polyclads to kill half of the bivalve population in field experiments was approximately 4.5 days. A simple disabling (an attack by the polyclad on the adductor muscle of the mussel) was shown to be sufficient to cause irreversible changes leading to mortality. Furthermore, disabling and mortality were found to be linearly correlated. The importance of mucous secretions, pharyngeal type and body musculature in supporting predation by polyclads is discussed. We suggest that measures to control the polyclad pest could incorporate the control of this flatworm's embryonic and postembryonic developmental stages.     

Water savings in irrigated potato production by varying hill-furrow or bed-furrow configuration

Current agronomic practices for potato production in the irrigated areas of southern Alberta involve a hill/furrow configuration that was adopted from elsewhere, and designed to shed rainfall away from the hill and into the furrow. However, the principal intent of supplemental irrigation is to capture as much of the applied water into the hill, where the potato tubers and roots are located, and minimize water accumulating in the furrow. A three-year project began in 2006 to quantify the potential irrigation water savings of altered hill shapes for potato production. The three treatments (standard hill, flat-topped hill, and double-planted wide-bed) were arranged in a randomized strip plot design replicated four times. Soil water in each treatment was generally kept between 60 and 90% of available. A fourth treatment, triple-planted wide bed, was added to the project in 2008. The irrigation requirements to maintain the treatments were 487, 442, and 449 mm for the standard hill, flat-topped hill, and double-planted bed, respectively, in 2006 and 442, 408 and 411 mm for the same treatments in 2007. This translates into approximately 10% less irrigation water required for the flat-topped hill shape compared to the standard hill shape. The flat-topped hill shape required 5.0% more irrigation than the standard hill in 2008, but the double and triple-planted wide beds required 8.0 and 9.9%, respectively, less irrigation water than the standard. Although not always statistically significant, water use efficiency was greater in all years for the altered bed shapes compared to the standard hill geometry. Greater water use efficiency can be interpreted as more of the applied water infiltrated into the hill, where the potato plant could use it for transpiration and tuber development. Total yield was greater in 2006 for both the flat-topped hill (72.3 Mg ha⁻¹) and wide-bed hill (69.2 Mg ha⁻¹) compared to the standard hill (61.4 Mg ha⁻¹); however, the treatments were not significantly different. Significantly greater marketable yield was realized from the flat-topped hill treatment in 2006. This treatment also had a significantly greater number of marketable size tubers. In 2007, there were no significant differences in total yield; however, the standard and flat-topped treatments had a significantly greater number and yield of tubers in the 113-170 g size category. Significant differences in total yield were found in 2008. The triple-planted wide bed had significantly greater yield in the smaller size categories compared to the standard treatment and significantly greater total tuber numbers than the other treatments, but the increase was in the smaller size categories, less than 170 g. There were no significant differences among the treatments in yield or total number of tubers in the size categories greater than 171 g in 2008.     

Effects of Lactic Acid Bacteria and Citrus Essential Oil on the Quality of Vacuum-Packed Sea Bass (Dicentrarchus labrax) Fillets During Refrigerated Storage

The preservative effect of refrigerated and vacuum-packed sea bass (Dicentrarchus labrax) fillets inoculated with four mixtures of lactic acid bacteria (LAB) (Lactococcus lactis, Lactobacillus plantarum, and Carnobacterium piscicola) and incorporated with citrus essential oil (CEO) was evaluated on the basis of microbiological and biochemical analysis.

Initially, sea bass fillets showed high nutritional quality. During refrigerated storage, lipid contents did not show a significant decrease in any fish fillets; meanwhile, important proteolysis was observed in untreated control. In addition, results indicated that both CEO and LAB strains exhibited antimicrobial activity against spoilage, pathogenic, and fungi flora. Moreover, the total volatile bases (TVB-N) values were higher in control fillets, and the lowest TVB-N values were observed in Control CEO and C3 + CEO (30.47 ± 0.00 and 32.29 ± 1.12 mg TVB-N/100 g, respectively). Also, the levels of biogenic amines increased in all fillets without exceeding the upper limit of acceptability except for untreated control (sum of about 1396.63 ppm). Furthermore, this combined treatment ameliorated the muscle liquid-holding capacity, which improves technological properties.

Overall, this treatment may open new promising opportunities for the biopreservation of fish products by enhancing the period of storage of refrigerated and vacuum-packed sea bass fillets.     

Importance of dietary arachidonic acid for the growth,survival and stress resistance of larval European sea bass (Dicentrarchus labrax) fed high dietary docosahexaenoic and eicosapentaenoic acids

Together with docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), arachidonic acid (ARA) is being considered to be an essential fatty acid in marine fish larval diets. The objective of the present study was to determine the importance of dietary ARA levels for larval European sea bass performance, when EPA and DHA are also present in the diet. Eighteen‐day‐old larvae were fed, for 14 days, gelatine‐based microdiets containing the following ARA levels: 0.3%, 0.6% or 1.2%. Elevation of dietary ARA up to 1.2% showed a positive correlation with larval survival and a significant improvement in the specific growth rates, body weight and total length. Arachidonic acid was efficiently incorporated into larval lipids, even at a higher proportion than that in the diets. Increased accumulation of ARA did not affect the incorporation of DHA or EPA from the diet into larval total lipids. A significant positive correlation was found between dietary ARA levels and survival after handling stress, indicating the importance of this fatty acid in sea bass larvae response to acute stressors. The results show the importance of ARA for sea bass larvae, but higher dietary levels should be tested to determine whether there is a negative effect of ARA in sea bass as reported for other species.     

奥尼罗非鱼5种组织中4种同工酶的研究

用聚丙烯酰胺凝胶垂直梯度凝胶电泳法对奥尼罗非鱼肾脏、肝脏、眼睛、肌肉和心脏等5种组织的酯酶(EST)、乳酸脱氢酶(LDH)、苹果酸脱氢酶(MDH)、超氧化物歧化酶(SOD)进行了初步研究,并分析了这4种酶的同工酶位点及酶谱表型。结果表明:奥尼罗非鱼的4种同工酶系统具有明显的组织特异性;EST由7个基因位点编码;LDH酶带多于大多数硬骨鱼典型的5条酶带;MDH和SOD都具有线粒体型和上清液型2种类型。     

点带石斑鱼不同组织同工酶的研究

运用聚丙烯酰胺垂直梯度凝胶电泳法对点带石斑鱼7种组织（眼睛、肌肉、心脏、肝脏、肾脏、尾鳍、脾脏）的4种同工酶（EST、SOD、LDH、MDH）进行了初步研究，并对4种同工酶的同工酶位点及其酶谱表型进行了分析。结果表明，点带石斑鱼的4种同工酶都具有不同程度的组织特异性：EST由4个基因位点编码，具有多态现象；肌肉SOD与其它组织SOD的差异最明显；眼睛LDH与其他组织LDH的差异最明显；MDH具有线粒体型（m-MDH）和上清液型（s-MDH）两种类型。     

基于mtDNA-COⅡ基因序列对中国南海裸胸鳝属鱼类分子系统进化关系的研究

采用聚合酶链式反应直接测序法,获得细斑裸胸鳝、黄纹裸胸鳝、云纹裸胸鳝、黑点裸胸鳝、褐裸胸膳5种裸胸鳝属鱼类的细胞色素氧化酶Ⅱ(cytochrome oxidaseⅡ,COⅡ)基因序列(691 bp)。结合GenBank上蠕纹裸胸鳝COⅡ同源序列,采用多个生物软件对6种裸胸鳝属鱼类序列变异和碱基组成进行分析,共发现196个核苷酸位点存在变异(28.36%);计算了它们的相对遗传距离、转换/颠换比等遗传信息指数,6种裸胸鳝属鱼类的序列差异为0.012~0.199,其中云纹裸胸鳝与褐裸胸鳝的序列差异最大,为0.199,细斑裸胸鳝与黄纹裸胸鳝序列的差异最小,为0.012;总体来说,序列中的转换明显多于颠换,转换和颠换的比值(Ts/Tv)为2.7;以长鳝为外群构建NJ、ME、MP系统树,长鳝分为独立的一支,6种裸胸鳝为另外一支,分为3个平行进化的分支。     

Regional and maturational effects on essential oils yields and composition of coriander (Coriandrum sativum L.) fruits

The composition of volatile components of the essential oils extracted from fruits of coriander (Coriandrum sativum L.) growing in two different Tunisian regions in both Menzel Temime and Borj El Ifaa was studied by GC and GC–MS. The highest oil yields were observed at final stages of maturity: 0.324 ± 0.09% and 0.327 ± 0.08%, in Menzel Temime and Borj El Ifaa, respectively. Essential oil yields were highly (P < 0.001) affected by the growing region, stages of maturity and their interaction. Essential oil composition changed significantly (P < 0.05) among the different stages of maturity and growing region. Linalool and geranyl acetate were the main compounds at full fruit maturity in the two studied regions. Growing region, stages of maturity and their interaction had a strong effect (P < 0.001) on 35 compounds. α-Pinene, sabinene, limonene, γ-terpinene, cis-dihydrocarvone and geranial were insensible to the regional factor.