A case study of the disappearance of Arius tenuispinis (marine catfish) in the vicinity of Visakhapatnam due to mechanised fishing

Visakhapatnam is on the eastern sea board of India (17 degree 40' N and 83 degree 15' E) having a continental shelf of 45 km width which is provided with a polychaete rich, silty clay sea floor to a distance of 15 km and beyond, from the shore. Repeated trawling by a large number of trawlers over an area of 900 sq.km (30 x 30) resulted in the hardening of the substratum to the extent of making it uninhabitable to the polychaetes and polychaete feeding fish. The shoaling and strictly demersal marine catfish, Arius tenuispinis, which is a prolific polychaete feeder on the fishing grounds off Visakhapatnam, has been on the decline since 1979. The catch rate of fish dropped from 9.7 kg/boat per day in 1979 to 2.6 kg by 1985-86. In the bottomset gillnets, the catch per net dwindled from 4.4 kg in 1973 to 0.04 kg by 1985-86. The species has virtually disappeared from the fishing grounds off Visakhapatnam and further north, as a results of the cumulative effect of overfishing with trawlnets and bottomset gillnets. It is further aggravated by the hardening of the sea floor on these grounds due to repeated trawling over a narrow zone.

On the identification of the early developmental stages of clupeiform fishes from Indian waters

Among about 65 species of clupeiform fishes present in the seas around India, most are distributed along both the east and west coasts and have similar spawning seasons and spawning grounds. The most difficult problem experienced with regard to the identification of their early developmental stages is the overlapping sets of diagnostic features among many species within the same genus as well as among species belonging to two or more genera. From studies carried out recently, the present paper sites a few instances wherein certain subtle characters have been used for distinguishing the early developmental stages of a few allied species.

毛乌素沙地四种关键植物幼苗出土及生长对沙埋和水分的响应

飞播是毛乌素沙地植被恢复与重建的重要手段。但此项技术仍存在一些问题，如飞播后成苗率较低等。柠条(Caragana korshinskii)、羊柴(Hedysarum laeve)、籽蒿(Artimisia sphaerocephala)与油蒿(Artimisia ordosica)是毛乌素沙地广泛分布的物种，也是飞播的主要物种。本文以飞播植被恢复技术为突破口，研究沙埋和土壤水分对种子萌发，幼苗出土和生长的影响，探讨幼苗出土和生长对沙生环境的适应对策。对采用合适的物种进行生态工程建设，提高生态工程的稳定性及可持续性具有重要意义。同时，本项研究有助于加深半干旱区植物对沙生环境适应机理的认识。 以上述4种植物为研究对象，设定7个沙埋深度和9个水分梯度，研究种子萌发和幼苗出土对沙埋和单次供水的响应。设定7个沙埋深度，选择3个沙丘部位，研究沙丘不同部位对植物种子萌发的影响。设定6个沙埋深度、4个水分梯度，研究两种蒿属植物幼苗生长对不同沙埋和供水的响应。得出如下主要结论： (1) 对于种子质量相对较大的柠条和羊柴而言，在一次性10-20 mm供水量条件下，幼苗主要在0.5-2 cm埋藏深度之间出土，但在埋藏深度为5 cm时这两个物种仍有少部分幼苗能够出土;对于种子质量相对较轻的油蒿和籽蒿而言，在一次性10-20 mm供水量时，幼苗主要在0.5 cm埋藏深度出土，油蒿和籽蒿幼苗在埋藏深度为1.5和2 cm时不能出苗。沙埋深度为0.5 cm时，4个物种出苗率较高、出苗时间较短、出苗速率较快。 (2) 实验期内(30天)在一次性供水量分别为5、7.5和7.5mm时，柠条、羊柴和油蒿出土幼苗全部死亡;在一次性供水量高于15-20 mm时，出土幼苗死亡率低于50%;籽蒿在供水量高于10 mm时出土幼苗死亡率低于50%;随供水量的增加4个物种出土幼苗的死亡率降低。 (3) 结合毛乌素沙地降雨特点与本文实验结果，0.5 cm的沙埋及7.5 mm以上的单次降雨量是上述4种植物自然条件下出苗较高的重要条件。 (4) 在沙丘顶部，2-7 cm沙埋深度之内各个物种不同沙埋深度的种子萌发率差异不显著。沙丘背风坡中部和底部，4个物种在沙埋深度为1 cm时的种子萌发率均显著高于5、7 cm时的萌发率。当沙埋深度为1-5 cm时，柠条和羊柴种子在坡面不同位置的萌发率均高于20%，且显著高于7 cm沙埋深度时的萌发率。在背风坡底部时，柠条、羊柴、油蒿和籽蒿的种子萌发率达到最大值，分别为45.2±3.27%、48.4±5.21%、20.8±4.63%和22.4±4.83%。4个物种的种子萌发率从沙丘顶部到背风坡中部到底部呈递增趋势，表明背风坡中部和底部的环境条件要比顶部更适合种子萌 发。 (5) 部分沙埋促进幼苗生长。2种蒿属植物幼苗在沙埋深度为0.25、0.5 H时比在0、0.75 H时具有更高的生物量、叶面积、相对生长速率（RGR）和净同化速率（NAR）。在75 mm/月供水量时，油蒿幼苗具有较高的生物量和叶面积，但当供水量达到100 mm/月时其幼苗生长受到抑制。油蒿幼苗在遭遇较深（0.5、0.75 H）沙埋时的根冠比要显著高于未沙埋幼苗的根冠比;籽蒿幼苗根冠比在不同沙埋条件下没有显著变化。籽蒿幼苗在50 mm供水量时具有较高的RGR。油蒿幼苗在75 mm供水量时具有较高的RGR和NAR。

沙埋与供水对毛乌素沙地两种重要植物幼苗生长的影响

近年来，土地荒漠化（ Desertification）及其防治已成为世界各国政府及科学界广泛关注的社会与环境问题。毛乌素沙地是我国荒漠化发展的中心地区之一。荒漠化不仅长期制约着地方经济的发展，同时也不同程度地影响着黄河中下游等地区的生态环境。因此，毛乌素沙地退化生态系统的恢复重建势在必行。沙埋与水分是该地区重要的生态因子和限制因子。柠条（Caragana korshinskii ）和羊柴（Hedysarum laeve ）作为该地区广泛分布的物种，经常用于我国北方干旱、半干旱区的生态恢复。因此，本文以这两个物种为研究对象， 探讨不同的沙埋与供水对两种植物幼苗存活与生长的影响。该研究对深化与丰富植物对沙生环境适应的生态学机理认识， 进而对采用合理的方法进行荒漠化防治及当地生态系统恢复重建具有重要的理论与实际意义。 以柠条（Caragana korshinskii ）和羊柴（Hedysarum laeve ）这两种植物幼苗为研究对象，人工控制6 个沙埋深度、5 个沙埋时间和4 个水分梯度，研究它们对不同沙埋深度和供水量的响应。结果表明：适量的沙埋(0.25~0.50 H 沙埋)与供水(柠条50 mm/月，羊柴75 mm/月)可以促进幼苗生长，过量的沙埋与供水则会抑制生长甚至导致幼苗死亡。柠条幼苗在50 mm/月供水， 0.25、0.50 H 沙埋， 羊柴幼苗在75 mm/月供水，0.25、0.50 H 沙埋下具有较高的生物量、叶面积、相对生长速率和净同化速率；幼苗在1.0 H 和1.25 H 沙埋下全部死亡。供水量较小、沙埋较浅时，两种植物根冠比均较高；当供水量最大时，柠条幼苗根冠比在沙埋最深和没有沙埋时较大，而羊柴幼苗根冠比仍在没有沙埋时最高。

Relative abundance and diel variation of zooplankton from south west coast of India

Relative abundance and diurnal variations of zooplankton from six anchor stations along Kerala coast were investigated. Samples were collected during April-May 1988 at three hour intervals from depths varying between 15 and 40 m from the traditional fishing grounds of Kerala coast. Average biomass values ranged from 45-95 ml 100/mˉ³. Increase in zooplankton at night was discernible at most of the stations and the highest biomass noticed was 131 ml 100/mˉ³. Copepods formed the most abundant group, of which calanoids predominated. A swarm of the hydromedusan species, Aequorea conica, (181/mˉ³) was seen at night. Quantitative and qualitative variations of various zooplankton groups from six stations in relation to selected physicochemical factors are discussed. Maximum fish larvae were observed in the night samples. Relatively high abundance of sardines, carangids and flat fish larvae in the collections is in agreement with the predominance of fish catch from the area of study.

Assessment of Saurida tumbil (Bloch) stock in the northwest continental shelf water of India

Based on the data collected from New Ferry Wharf, Sassoon Dock and exploratory survey of MFV Saraswati on the Northwest coast of India, the growth, mortality, population and stock parameters of Saurida tumbil is reported in the present communication. The Von Bertalanffy growth function (GF) parameters for growth on length were found to be L∞=49.8 cm, K=0.96/year, t0 = -.141 year. The length at recruitment (lr) is 80 mm. (tr=.167 year) while the length at first capture (lc) for the commercial trawl fishery is 100 mm (tc=0.25 year). The annual fishing mortality coefficient (F) for 1983-85 was 0.43, the natural mortality coefficient (M) was 1.33 and the exploitation ratio (E) was 0.25. The yield per recruit (Y/R) attained the maximum of 54.99 g at F=1.091 for E=0.45 for the present tc at 0.25 year. The annual total stock (P) and standing stock (P) in the exploitation portion at the inshore grounds to a depth of about 50 m were estimated to be 12,811 tons and 6,034 tons respectively. The average annual yield of 2,635 tons at the present F=0.439 (E=0.247) was less than the maximum sustainable yield (MSY) for 3,331 tons attainable from the inshore grounds at E=0.45.

The riverine fisheries of large sized siluroids with special reference to Aorichthys seenghala (Sykes)

The significance of large siluroids in dynamics of riverine fish catch composition pinpointed the need to appraise that i) fisheries; ii) status in riverine fisheries; and iii) factors influencing their fisheries with special reference to Aorichthys seenghala (Sykes). The investigations were carried out in the middle stretch of Ganga river system around Allahabad. The study concluded that although, catch of large siluroids had declined but their share in riverine catch increased. The same was true for A. seenghala. The increase in fishing intensity in A. seenghala breeding grounds was one of the evident indicators of fishing stress on the fish. Strong seasonality was observed in its catch over the year. The wanton killing of breeding population during premonsoon and juveniles during postmonsoon may be attributed for this seasonality and decline in its catch. The fishing stress needs to be diverted through some more lucrative option to save its fisheries. Collection of young ones from the nest, during breeding months and their subsequent culture may be one of the conservation measures. It would also generate additional employment for fishers and defer wanton killing of brood stock.

Wadge Bank trawl fishery studies. Pt. 4. An analysis of the length frequency measurements of the sea bream (Lethrinus nebulosus) made in 1949 and 1953 to 1958

Length frequency distributions of the sea bream collected during the period 1953 to 1958 have been analysed. The increase in average sizes of the sea bream with depth suggests a movement to deeper waters with increase in size. By numbers, the sea bream is more abundant between 21 and 30 fathoms than in deeper areas. The recruitment was continuous and regular. There is no sign of entry or progression of a dominant brood throughout the period under study. Length frequency distribution shows three distinct modes. The first mode occurs regularly but does not progress beyond 40cm, recruitment being balanced by natural and fishing mortality. The other two which are not regular are probably the result of fishing outside regular areas. Short sections of “growth” lines which fit into one another when extrapolated, are evident. The larger lines obtained by extrapolation are parallel to one another. These tentative "growth lines" indicate that this species which enters the fishing grounds, when 15 cm or larger in length are exploited by the trawl fishery for a period of three to four years. This species appears to be six months old when it enters the fishing grounds and increases in length by about 37.5 cm in the next 30 months. Later growth slows down. The average size of the specimens sampled continued to get smaller from 1953 till 1957. It is shown that this reduction in size is due to increased fishing effort.

Wadge Bank trawl fishery studies. Pt. 5. Rational exploitation of the resident demersal stock

The general history of the trawl fishery of the Wadge Bank off Cape Comorin, South India (Fig. 1), the nature and composition of its demersal fish population, and the present state of its fishery has been given by various authors (Malpas 1926, Pearson and Malpas 1926, Sivalingam and Medcof 1957, Medcof 1963, Mendis 1965a, 1965b, Sivalingam 1966a, 1966b, 1969a and 1969b). It has been shown earlier (Sivalingam and Medcof 1957, Sivalingam 1969a) that the Wadge Bank stock is made up of two groups. The resident stock which is present on the fishing grounds throughout the year and the migrant stock that appears on the fishing grounds only during the southwest monsoon months. The object of this paper is to discuss the effect of fishing on the resident stock between 1945 and 1962 and based on the information available; assess the maximum sustained yield of the resident stock. The "Bigfish" of the resident stock is the mainstay of the Wadge Bank trawl fishery (Sivalingam 1969a) and it will be shown that this stock has been overexploited from 1953 to 1957. The first sign of recovery was evident in 1960 and continued till 1962. The data since 1962 are not available to the author for analysis. It has been reported by Mendis (1965b) that considerable expansion of the trawler fleet was anticipated in 1966, and if so, the history of the fishery from 1953 to 1957 may be repeated. The assessment presented in this paper should form a rational basis for management programs.

Sirahu Valai: a passive fishing gear in Ceylon

There are many types of passive fishing gear in use in the estuarine waters and lagoons in Ceylon such as the stake seine net or Kattudel, the tat trap or Jalcottu and the wing net or Sirahu valai. Of these Siraku valai is very popular in the shallow and near shore areas of the sea in north Ceylon. Sirahu valai is popular since it is relatively more economical, less time consuming and more efficient than other forms of fishing gear in shallow waters. More over the fishermen do not have to remain in the fishing grounds while his gear is fishing. Pearson (1923) described this gear as a stake net having a complicated arrangement. Sirahu valai is also referred to as Siraku valai or Kurukku valai.

Relatório do cruzeiro realizado no Banco de Sofala no barco "Meleia" em Agosto de 1981: fauna acompanhante de camarāo

This cruise report describes the Sofala Bank (Mozambique) crustacean stocks and the fish by-catch. A survey was made of the stock assessment of demersal fish with commercial interest, fishing grounds, biology and distribution of the most abundant demersal fishes and the specific composition of trawl catch areas.

Demersal fishery resources of Sri Lanka and its present level of exploitation with special reference to off-shore and deep-sea waters

Following a brief review of development of demersal fishing off Sri Lanka, the author reviews the fishing grounds of the Wadge Bank, the Pedro Bank, and the Mannar Bank. He reviews the deepwater trawling fisheries particularly in relation to the 1972 survey conducted by the 'Optimist' and also small boat trawling in coastal waters. Lastly he considers handlining for groundfish, which is principally conducted by fishermen operating traditional craft.

Impact of community-based fisheries management practices on production and species diversity in Turag-Bangshi basin floodplains in Kaliakoir, Gazipur, Bangladesh

The study was conducted to investigate the communities perception and compliance to community-based fisheries management (CBFM) in Turag-Bangshi floodplains under Kaliakoir, Gazipur District. Measures such as ban on use of the harmful fishing gears, seasonal fishing closure, halt of fry fishing, halt of dewatering of beels and the impact of establishment of sanctuaries on fish production and species diversity were introduced by MACH project. Almost all members of the communities in Turag-Bangshi MACH (Management of Aquatic Ecosystem through Community Husbandry) site welcomed the introduction and complied with the implementation of all management measures which helped stopped use of harmful fishing gears, ensured survival and breeding of brood fish in the rainy season, protected and allowed fry to grow big, restored lost and degraded fisheries and organized communities for sustainable development of the fisheries. A total of 51 species of fishes were found in Makosh beel (natural depression). Among these, small indigenous species (SIS) under Cyprinidae family (Puntius sophore) was the most dominant. Many species available in the past recorded disappeared from the Makosh beel due to loss of habitat and industrial pollution that damaged spawning and nursery grounds of fish. Introduction of some selective native endangered species (Nandus nandus, Notopterus notopterus, Ompok pabda and Labeo calbasu) by MACH in the Turag-Bangshi water bodies increased diversity of species from 82 to 95. Over a period of five years during MACH intervention, the average production remained nearly 200% higher than the baseline production of 57 kg/ha to present 207 kg/ha due to maintaining sanctuaries and the closed fishing seasons. Per capita daily fish consumption of the surrounding communities also increased by 78% (from 27 to 48 g/person/day) which is much higher than the national average fish consumption in Bangladesh. The implementation of community-based MACH project management measures substantially improved fish habitat, production, consumption and socio-economic conditions of the surrounding communities. The model can be used to improve the floodplains of Bangladesh.

Natural diet of penaeid prawns in the coastal waters of Mumbai

Foregut contents of eight commercially important species of penaied prawns namely Penaeus merguiensis, Metapenaeus affinis, M. monoceros, M. brevicornis, Parapenaeopsis stylifera, P. hardwickii, P. sculptilis and Solenocera crassicornis were investigated from inshore, nearshore and offshore fishing grounds of Mumbai. Feeding intensity and index of preponderance (IP) of the dietary items were compared statistically for the species, sexes, fishing areas and maturity condition of females. All the species except M. monoceros and P. sculptilis showed that females were better fed than males. The feeding intensity in the three depth-zones was different for M. affinis, M. brevicornis, M. monoceros, P. hardwickii and S. crassicornis, and uniform for P. merguiensis, P. stylifera and P. sculptilis. Acetes spp., prawn remains, polychaetes, benthic crustaceans, foraminifers and fish remains were the important food items of the prawns. Dietary comparison between the two sexes of the species did not show any difference, but mature females of M. monoceros and P. sculptilis had different diets. Comparison of food items for all the species together showed significant difference between the three areas. Crustacean diet was the favorite in the inshore and nearshore, and polychaetes in the offshore waters. All the species except P. hardwickii showed difference in their dietary composition in the three depth-zones. It is concluded that these coexisting species are primarily carnivorous and exhibit diverse food preferences in different depth-zones by browsing on interstitial organisms, chasing epipelagic prey, raptorial predation, scavenging on dead organisms or adopting different temporal abundance to avoid inter-specific competition for food.

Losses in self-oscillating ballasts for electrode-type compact fluorescent lamps

Commercially available integrated compact fluorescent lamps (CFLs) use self-resonant ballasts on grounds of simplicity and cost. To understand how to improve ballast efficiency, it is necessary to quantify the losses. The losses occurring in these ballasts have been directly measured using a precision mini-calorimeter. In addition, a Pspice model has been used to simulate the performance of an 18 W integrated CFL. The lamp has been represented by a behavioural model and Jiles-Atherton equations were used to model the current transformer core. The total loss is in close agreement with measurements from the mini-calorimeter, confirming the accuracy of the model. The total loss was then disaggregated into component losses by simulation, showing that the output inductor is the primary source of loss, followed by the inverter switches. © 2011 The Institution of Engineering and Technology.