Nutrient digestibility of angling baits for carp, Cyprinus carpio, with implications for groundbait formulation and eutrophication control

Abstract  To evaluate the suitability of angling groundbaits as a fish feed and the potential for nutrient loss, the macronutrient digestibility of four groundbaits was investigated in carp, Cyprinus carpio L., using a sieving method of faeces collection and chromic oxide. Apparent digestibility coefficients (ADCs) of protein and lipids were >80% for all angling baits. ADCs of nitrogen-free extracts and phosphorus (P) differed significantly between the test diets, probably because of divergent feed compositions and ingredient treatments. The generally high digestibility estimates indicated that fish feeding on angling groundbait will benefit from this food source. The differences in nutrient digestibility suggested that type of groundbait and ingredient used will have a major effect on potential eutrophication and fish production caused by groundbaiting. The principle of groundbaits to protect the environment should be to minimise the P-content of the groundaits and maximising P-digestibility and P-retention efficiency.     

Relationships between catch and effort in Fijian multispecies reef fisheries subject to different levels of exploitation

Abstract The catch-per-unit-effort (CPUE) and value-of-catch-per-unit-effort (VPUE) of reef-associated fish species from six Fijian native fishing grounds ( qoliqoli ) subject to different fishing intensities were determined using records of fishing activity from a voluntary logbook scheme. Line and spear fishing techniques were used for more than half the total fishing time (h person^-1 d^-1) in all qoliqoli , and yet the favoured technique in a given qoliqoli was frequently less efficient (lower CPUE) than other techniques. The popularity of relatively ineffective fishing methods implies that fishermen did not always attempt to maximize their catch rates. To compare fishing effort in different qoliqoli , all effort was rescaled on the basis of its recorded efficiency (measured as multispecies CPUE) and expressed as hours equivalent to boat-based spear fishing over coral by day to catch fish for sale. Total fishing intensity in the six qoliqoli ranged from 72 to 4310 h km^-2 reef year^-1. The relationship between catch and effort was linear at all fishing intensities, suggesting that the qoliqoli were all fished on a sustainable basis. Furthermore, whilst there was a significant difference in CPUE and VPUE between the one or two qoliqoli with lowest fishing intensity and all the others, there were no significant differences between these other qoliqoli in terms of the VPUE of the saleable multispecies boat catch or the CPUE of species from piscivorous and carnivorous genera ( Epinephelus, Lethrinus and Plectropomus ) which the fishermen prefer to catch.     

2010—2019年江苏省渔业船舶水上安全事故分析及对策建议

依据中国渔政指挥系统江苏省渔业船舶水上安全事故的统计资料,对2010—2019年事故的发生时间、事故起数、死亡人数、事故类型和事故等级等方面进行了统计分析。结果表明,江苏省渔业船舶水上安全事故以一般等级事故居多,事故发生时间呈现一定规律性,渔船自身安全隐患突出,从业人员岗位技能不足,渔船安全管理责任不到位。基于分析结果,提出压降一般等级事故,遏制较大等级以上事故,提高风险管控和事故防范能力的对策建议。     

基于无线发射接收组件的鱼塘增氧机自动控制系统

通过分析和研究国内外鱼塘增氧机自动控制的实现方法,设计了鱼塘增氧机自动控制系统.该系统以无线发射接收组件为核心,根据对鱼塘溶氧含量、噪声和温度的检测决定增氧机的启停.介绍了发射电路和接收电路的工作原理图,对工作原理进行了说明,并且详细论述了各种参数的检测方法;为了保证控制的效果以及系统工作的稳定性、可靠性,提出了电路的安装方法.     

基于SESAM的游钓船动力响应研究

由于游钓船没有明确的设计规范,为了确保游钓船的作业安全,采用SESAM系统的PatranPre模块对游钓船进行水动力建模,并在HydroD模块中进行了运动与波浪载荷响应计算,对其水动力特性进行分析。     

我国综合养鱼生态模式及其发展思路

我国主要的综合养鱼生态模式有渔农综合经营型,渔牧综合经营型,渔、农、牧综合经营,农庄式立体种养生态系统等。然而劳动力素质限制了其综合利用水平的提高,水质污染影响渔业可持续发展,综合养鱼生态系统基础研究滞后及渔业产业化经营程度不高均是亟待解决的问题。并指出了促进综合养鱼生态模式的发展思路。     

北京市水生动物防疫工作现状和发展对策

当前我国渔业正处于从传统渔业向现代渔业转变的关键时期,坚持用科学发展观指导新时期水产养殖业发展,是促进渔业经济增长方式转变,保证水产养殖持续健康发展的前提。应将以人为本的科学发展观、人与自然和谐发展、循环经济、资源节约和环境友好的思想、理念,落实到水产养殖业未来的发展中。     

Decreasing shrimp (Pandalus borealis) sizes off Newfoundland and Labrador – environment or fishing?

During the 1990s, carapace length statistics including minimum size caught (L_min), mean male and female lengths, size at sex transition (L₅₀) and maximum size (L_max) of northern shrimp (Pandalus borealis) decreased in commercial and survey catches off Newfoundland and Labrador. Decreased growth rates caused by decreases in per‐capita food availability due to large population increases, exacerbated by increased metabolic demands from higher water temperatures in the mid‐1990s, appear to be the main cause of the size decrease. Fishing could have had an accelerating effect on environmentally driven decreases in shrimp growth and size by ‘cropping’ the largest shrimp from the population. The greatest decreases in shrimp size occurred in Hudson Strait and the adjacent northern shelf, the area which also has the highest densities and largest shrimp. We hypothesize that the greater size decrease here resulted from decreased primary production from decreased nutrient flux into the euphotic zone, caused by increased atmospheric warming, freshwater runoff and stratification during the warming trend of the 1990s.     

Effects of intensive fishing on the perch population in a large oligotrophic lake in eastern Finland

The perch population in Lake Höytiäinen was intensively fished to reduce the density of the population and hence also the predation pressure by perch on vendace larvae. A hypothesis suggests that this predation can prevent recovery of commercially important vendace stock from a state of low-density. In the 1990s the density of the perch population in Lake Höytiäinen has increased, while the vendace stock has been sparse. Intensive fishing was conducted by professional fishermen with a paired bottom trawl, seine net, hoop net and small fish traps and by recreational fishermen with small fish traps. The size of perch population during the intensive fishing period was studied by test fishing with multi-mesh gillnets and the Leslie method in which trawl YPUE was regressed on the cumulative yield. The results suggest that the population size clearly diminished in the area where the fishing pressure was strongest. YPUE of test fishing decreased ca. 30% whereas the Leslie method gave almost a decrease twice as large as that of the former. Mean weight of perch increased in the trawl and test fishing catches during the intensive fishing period. The most effective fishing gear was trawl (62% of the total yield), but importance of trap net fishing by recreational fishermen was also high as they caught 22% of the total yield.