The Social Aspects of Fishing Effort

While economic literature inspired by the “tragedy of the commons” has emphasised people’s tendency to increase fishing effort beyond desirable levels, sociologists and anthropologists who have studied the social aspects of fishing have often emphasised the capacity of these factors to restrict fishing effort. The article addresses the influence of social norms and communication on fishing effort in an empirical study of the Atlantic blue whiting fishery. The data were generated at a time when this fishery had yet to see efficient quota regulations, and had been subject to a rapid growth in fishing effort, making it the largest fishery in the Atlantic. The article argues that social norms and communication patterns in the fishing fleet create a synergic effect of co-operation and competition on fishing effort. The article questions the view that social norms and communication necessarily represent a solution to the tragedy of the commons.

Monognathus berteli sp. nov. from the Indian Ocean (Pisces,Monognathidae)

A new deepsea monognathid species,Monognathus berteli, is described based on one specimen collected pelagically in the northwestern Indian Ocean at 1440–1018 meters of depth. LikeM. taningi andM. bertini, it belongs to the short-skulled species-group and has very long pectoral fins, but differs from these species by several meristic characters. The described specimen has a very long caudal filament (53% SL) which is not known from otherMonognathus. However, the fragile filament is not used as a diagnostic character since it could easily be broken.     

热带印度洋黄鳍金枪鱼渔场时空分布与温跃层的关系

根据Argo浮标剖面温度数据重构热带印度洋各月月平均温跃层特征参数,并结合印度洋金枪鱼委员会(IOTC)黄鳍金枪鱼延绳钓数据,绘制了月平均温跃层特征参数和月平均CPUE的空间叠加图,用于分析热带印度洋黄鳍金枪鱼渔场时空分布和温跃层特征参数的关系。结果表明:热带印度洋温跃层上界深度、温度和下界深度,以及黄鳍金枪鱼中心渔场分布都具有明显的季节性变化特征,黄鳍金枪鱼中心渔场分布和温跃层季节性变化有关。在东北季风期间,高值CPUE渔区的温跃层上界深度的范围为30-40m,超过70m的渔区CPUE值普遍偏低;在西南季风期间温跃层上界最深达到120m。在东北季风期间,高值CPUE渔区温跃层下界深度不超过200m,在西南季风期间,深度会超过300m。在东北季风期间,高值CPUE渔区对应的温跃层上界温度都超过25℃,温度小于24℃的渔区CPUE值普遍较低;在西南季风期间,高值CUPE区域对应的温跃层上界温度范围变大,温跃层上界温度延伸到22℃,在22℃以下渔区CPUE值都很低。采用频次分析和经验累积分布函数计算其最适温跃层特征参数分布,得出黄鳍金枪鱼最适的温跃层上、下界温度范围分别是25-29℃和13-16℃;其上、下界深度范围分别为30-70m和140-200m。K-S检验结果表明,上述结论可靠。     

Multiple population structure of the giant mottled eel, Anguilla marmorata

The population structure of the giant mottled eel, Anguilla marmorata, was investigated with mitochondrial and microsatellite DNA analyses using 449 specimens from 13 localities throughout the species range. Control region F-statistics indicated the North Pacific (Japan, Taiwan, Philippines, Sulawesi), South Pacific (Tahiti, Fiji, New Caledonia, Papua New Guinea), eastern Indian Ocean (Sumatra), western Indian Ocean (Réunion, Madagascar), Ambon, and Guam regions were significantly different (Phi(ST) = 0.131-0.698, P < 0.05) while only a few differences were observed between localities within the South Pacific. These regions were roughly clustered in the neighbour-joining tree, although Ambon individuals were mainly divided into North and South Pacific groups. Analysis with eight microsatellite loci showed almost identical results to those of the control region, except no genetic difference was observed between the western and eastern Indian Ocean (F(ST) = 0.009, P > 0.05). The Bayesian cluster analysis of the microsatellite data detected two genetic groups. One included four North Pacific localities, and the other included eight localities in the South Pacific, Indian Ocean, and Guam, but Ambon individuals were evenly assigned to these two groups. These results showed that A. marmorata has four genetically different populations (North Pacific, South Pacific, Indian Ocean, Guam region). The North Pacific population is fully panmictic whereas the South Pacific and Indian Ocean populations have a metapopulation structure. Interestingly, Guam was suggested to be inhabited by a reproductive population restricted to that region, and the individuals from the North and South Pacific populations co-exist in Ambon.     

Biodiversity patterns in Indian Ocean corals, and effects of taxonomic error in data

Corals from 26 sites in the Indian Ocean, from numerous taxonomic sources, are analysed for distribution patterns after applying a consistent synonymy. The data set contains double the amount of distribution information used previously. Cluster analysis shows several contiguous regional groupings within this ocean, and no geographically dispersed groupings exist. Between-site species similarity correlates negatively with distance between sites. Coral species diversity and genus diversity plotted with latitude and longitude confirm that a band of high diversity stretches across the entire Indian Ocean, but that in this Ocean, unlike the Pacific and greater Caribbean area, there is no clear gradient with latitude at least up to the latitudinal limits of coral growth. About half the species are widespread throughout the Indian Ocean. Species frequency/distribution curves and cumulative frequency curves show that 150 species occur at only 2–4 sites. Multi-dimensional scaling (MDS) analysis using only these species confirms that they are important in forming sub-regional groupings which are superimposed on a general Indian Ocean homogeneity.The perennial problem of error in taxonomic data sets is examined. Increasing taxonomic error is introduced into the data using random methods. It is found that about 25% more error can be added to this data set before the relationship between similarity coefficient and geographical distance between pairs of sites is lost. Measures extracted from the clustering procedure using the original data and the data sets with added taxonomic error, show a sharp loss in cluster formation after addition of about 10 or 20% more error.     

Phosphate fractionation in mud bank sediments from the southwest coast of India

Mud banks are unique, occurring along the southwest coast of India. They are known as ‘Zones of Bio-rhythm’, providing shelter to abundant aquatic life. The cyclic variation of nutrients in this region provides a clue to the continued and enriched presence of a variety of fish. This study reports on the different forms of phosphate in the resuspended sediments collected during the seasons with and without mud banks from the above mentioned coastal zones. Applying sequential and parallel chemical extractions using eight different schemes, the major forms of phosphate namely exchangeable P, anion exchangeable P, carbonate bound P, labile and resistant organic P, Fe-, Al- and Ca bound P and hydrolysable P have been determined. Quantitatively, these fractions vary and exhibit seasonal fluctuations. The concentration of potentially available anion exchange P, together with resistant organic and hydrolysable surplus P, provide an explanation to the existing organic food web supporting the aquatic life. Sediment phosphate fractionation reflects the role of chemical speciation of nutrients in the propagation of mud banks and is indicative of the biogenic processes controlling the pathways of phosphate in these coastal waters. Editorial note: Because of the sudden, regrettable death of the senior author, Dr P. N. K. Nambisan, editing remained unfinished. The guest editor remains responsible for errors left in the text.     

Influence of environmental variability on breeding effort in a long-lived seabird, the yellow-nosed albatross

The provisioning parameters, breeding success, adult mass, andsurvival of yellow-nosed albatrosses were studied over 7 successiveyears at Amsterdam Island, southern Indian Ocean. We examinedthe ability of this long-lived seabird to adjust its breedingeffort under different environmental conditions and the fitnessconsequences in terms of survival and quality of offspringproduced. Provisioning rate and adult mass varied extensivelybetween years, and the lowest and highest values were associatedwith sea surface temperature anomalies. When waters aroundthe island were colder, adults were in good condition and broughtlarge meals at short intervals, whereas warmer waters resultedin lower provisioning rates, lower adult mass, and lighter chicksat fledging. Adult survival and fledging success were not affectedby sea surface temperature anomalies. Yellow-nosed albatrossesappear to be unable to adjust their breeding effort every season,and their differential breeding investment probably primarilyreflects different levels of food availability. Yellow-nosedalbatrosses are able to regulate their provisioning behavioraccording to the nutritional status of their chick only whenconditions are favorable. Birds appear to invest primarilyin their own future maintenance rather than in provisioning.They have a wide safety margin in body mass that limits mortalityrisks during good years as well as during poor years. However,during unfavorable seasons adults continue to provision chicksthat have a poor prospect of survival to breeding, withoutadditional survival costs for the parents. Favorable seasonstherefore have a high value in terms of fitness because ofthe high quality of the chick produced. We suggest that understandinghow long-lived animals optimize their provisioning behaviorand lifetime reproduction can only be achieved through studiesencompassing several contrasted seasons.     

Abundance of thraustochytrids and bacteria in the equatorial Indian Ocean, in relation to transparent exopolymeric particles (TEPs)

Thraustochytrid protists are often abundant in coastal waters. However, their population dynamics and substrate preferences in the oceanic water column are poorly understood. We studied the abundance and distribution of thraustochytrids, bacteria and TEPs in the equatorial Indian Ocean waters during September 2003, October 2004 and September 2006. Thraustochytrids and bacteria were abundant, suggesting high biological productivity of the region. Thraustochytrids were positively related to bacteria during October 2004 but not at other times, suggesting overlapping or varying substrate preferences at different times. Thraustochytrid and bacteria were positively related to TEPs only in a few stations during October 2004, but were mostly positively related to TEPs generated from in situ water in a roller table experiment. TEPs from natural samples during October 2004 had a much greater affinity to the lectin Concanavalin A than to Limulin compared with those in September 2006 and from the roller tank experiments. The chemical composition of TEPs might explain their relationship with thraustochytrids. Thraustochytrids averaged a higher biomass than bacteria in two of the three cruises, but were less frequent and more patchily distributed compared with bacteria.     

夏季西南印度洋叶绿素a分布特征

分析了2011年1月西南印度洋叶绿素a的分布特征及其粒级结构,并结合水动力学环境和营养盐数据探讨了其主要影响因素。结果表明,西南印度洋副热带涡流(IOSG)区表层叶绿素a浓度较低,不超过0.07 mg/m3,次表层叶绿素a浓度最大值所在水层较深,超过100 m;副热带聚集区(SCZ)表层叶绿素a浓度较高(0.164—0.247 mg/m3),次表层叶绿素a浓度最大值出现在50—70 m层。硝酸盐是该海区浮游植物生长的主要限制因素。微微型(pico)粒级的浮游植物占绝对优势,所有站位其对总叶绿素a的平均贡献率为71.1%,微型(nano)粒级次之(24.2%),小型(net)粒级所占比例最小(4.7%),其中IOSG区pico粒级对总叶绿素a的平均贡献率为77.9%,SCZ的pico粒级对总叶绿素a的平均贡献率为66.7%。IOSG区和SCZ海区之间水动力学环境的不同,可能导致了这两个海区叶绿素a的分布特征及粒级结构的较大差异。     

Fishing Behavior and Decision-Making in an Ecuadorian Community: A Scaled Approach

Debate over how people behave in an open access environment is ongoing in both the social sciences and natural resource management circles. Central to this debate is the question of driving forces behind decisions and behavior toward natural resources within a given area. Using data from an artisanal shrimping community in Ecuador, I demonstrate that behavior in an open access environment, measured in terms of fishing effort, is responsive to both economic and noneconomic factors, the nature of which depends on the temporal scale at which behavior is being measured—hourly, daily, or amount of gear over time. These findings suggest that much of the observed variation between previous studies and corresponding data sets may be a methodological artifact, and the ensuing debates ultimately a result of different methodologies and scales of analyses.