A comparison of trace element concentrations in cultured and wild carp (Cyprinus carpio) of Lake Kasumigaura, Japan

The concentrations of 13 elements were determined in the muscle, liver, intestine, kidney, and gonads of cultured and wild carp caught at two sites in Lake Kasumigaura, Japan, between September 1994 and September 1995. Despite having a reputation for being heavily polluted, the carp were not heavily burdened with metals. Our results suggest that despite their dietary differences, the wild and cultured fish were accumulating and distributing metals in the same manner and that aquaculture practices are not increasing metal concentrations in these fish. Metal concentrations were lowest in muscle, and did not exceed established quality standards for fish. The differences in metal concentrations between cultivated and wild carp are negligible and should pose no health problems for consumers of either type of fish.

Using mitochondrial nucleotide sequences to investigate diversity and genealogical relationships within common carp (Cyprinus carpio L.)

Direct sequencing of mitochondrial DNA (mtDNA) D-loop (745 bp) and MTATPase6/MTATPase8 (857 bp) regions was used to investigate genetic variation within common carp and develop a global genealogy of common carp strains. The D-loop region was more variable than the MTATPase6/MTATPase8 region, but given the wide distribution of carp the overall levels of sequence divergence were low. Levels of haplotype diversity varied widely among countries with Chinese, Indonesian and Vietnamese carp showing the greatest diversity whereas Japanese Koi and European carp had undetectable nucleotide variation. A genealogical analysis supports a close relationship between Vietnamese, Koi and Chinese Color carp strains and to a lesser extent, European carp. Chinese and Indonesian carp strains were the most divergent, and their relationships do not support the evolution of independent Asian and European lineages and current taxonomic treatments.

Use of pineapple juice for elimination of egg stickiness of common carp (Cyprinus carpio L.)

Four treatments including three different concentrations of pineapple solution (I %, 3%, 5%) and the traditional method (salt/urea/tannin solutions) were used to eliminate egg stickiness of common carp. With the traditional method, fertilization and hatching rates were 74.5% ± 1.2 and 70.2% ± 1.1, respectively. The highest fertilization rate (89.3% ± 0.7) and hatching rate (86.6% ± 1.4) were found with treatment of 1% pineapple juice solution and was significantly different from those obtained with other treatments (P<0.05). Using pineapple juice for desticking common carp eggs also reduced the time of egg handling from almost one hour required with the traditional method, to about three minutes, as well as increasing fertilization and hatching rate under hatchery conditions.

Observations on the effects of caged carp culture on water and sediment metal concentrations in Lake Kasumingaura, Japan

The concentrations of 24 elements in the sediment and associated water column were monitored at two sites, one an area of intensive cage culture of carp, the other a wild site far from known cage culture areas, in Lake Kasumigaura, Japan, between September 1994 and September 1995. The concentrations of most elements in Lake Kasumigaura are mostly sub-parts per billion, except those for Ca, Fe, K, Mg, Na, P, and Si. The concentrations of Cd, Co, Cu, Mn, Ni, Pb, V, and Fe in Lake Kasumigaura are higher than the values in Lake Mashu, Lake Shikotsu, and Lake Biwa, and comparable to the levels in open ocean. Statistically significant differences in metal concentrations were observed between the culture and wild sites, with metal concentrations consistently higher at the culture site. Although cage culture of carp in the Lake Kasumigaura system may be causing localized increase in metal concentrations in the sediments, we must treat the results with caution, since the concentrations of metals observed in the sediments in 1995 were lower than those observed in 1979 for all metals at both sampling sites. In conclusion, further study of the concentrations of metals in the lake as a whole must be undertaken before the differences between the culture and wild sites can be proved, or disproved, to be the result of carp culture.

Eri silk fibre attributes and sliver preparation

Eri silk produced by Philosamia cynthia ricini silkworm is a fibre not well-known to the silk industry, in spite of the fact that Eri silk is finer, softer, and has better mechanical and thermal properties than most animal fibres. Eri silk has a high commercial potential, as the host plants of Eri silk worms are widespread in diverse geographical locations, and the worms also have a higher degree of disease resistance than most other silk worms. Mills are often not aware of the properties of Eri for designing appropriate end products. Thus, Eri silk yarn is traditionally produced by hand spinning, and Eri silk usually ends up as material for handwoven shawls. The potential for bulk fibre processing and the development of soft luxurious novel Eri silk products is yet to be discovered. To better understand the material and its processing behaviour, Eri silk was characterised and cocoons were processed into tops through degumming, opening, and cutting filaments into different lengths, followed by a worsted spun silk processing route. Fibre properties such as fineness, crimp, strength and length at different processing stages up to combed tops were measured. The results indicate that staple Eri silk can be processed via the worsted topmaking route, using a cut length of 200 mm or 150 mm for filament sheets prepared from degummed cocoons.

The effect of seed morphology on the potential dispersal of aquatic macrophytes by the common carp (Cyprinus carpio)

1. The potential for seed dispersal by fish (ichthyochory) will vary among aquatic plants because of differences in seed size and morphology.

2. To examine how seed morphology influences the probability of dispersal by the common carp (Cyprinus carpio), we studied seed ingestion, retention time and subsequent egestion and germination of seeds of Sparganium emersum and Sagittaria sagittifolia, two aquatic plant species with similar sized but morphologically different seeds.

3. We compared dispersal probabilities between the two plant species, in which the probability of dispersal is assumed to be a function of the probabilities of seed ingestion, egestion and germination, and the dispersal distance is assumed to be a function of seed egestion rate over time.

4. We found that, although the soft seeds of S. sagittifolia had an approximately 1.5 times higher probability of being ingested by the carp than the hard seeds of S. emersum (83.15% ± 1.8% versus 56.16% ± 2.7%, respectively), the latter had an almost twofold higher probability of surviving the passage through the digestive tract (38.58% ± 2.7% versus 20.97% ± 1.5%, respectively). Patterns of seed egestion over time did not differ between the two plant species, despite the difference in seed morphology. Gut passage had a different effect on seed germination between plant species. Compared with non-ingested controls, seeds of S. emersum showed a 12.6% increase in germination and a 2.1 day acceleration in germination rate, whereas seeds of S. sagittifolia displayed a 47.3% decrease and 5.1 day delay, respectively.

5. Our results suggest that seed morphology affects the dispersal probability and postdispersal establishment, but not the dispersal distance, of aquatic plants that are dispersed by fish.

Strong population genetic structure and its management implications in the mud carp Cirrhinus molitorella, an indigenous freshwater species subject to an aquaculture and culture-based fishery

This study investigated population genetic structure and diversity of mud carp Cirrhinus molitorella, a species widely used in aquaculture and culture-based fisheries in China and Mekong River riparian countries. Seven newly developed and one published microsatellite DNA markers were used to analyse samples from six wild locations, four hatchery broodstocks and one farmed site from the Mekong, Red and Pearl Rivers. Significant genetic structure was detected in C. molitorella, with isolation-by-distance being a strong force in the Mekong. Pair-wise F_ST, Fisher's exact tests for population differentiation, permutation tests and individual-based structure analysis all support the recognition of a sample originating from Toul Krasaing Lake (Cambodia) and one between Kratie and Stung Treng (Cambodia) as distinct from the remainder of the sampled range. Samples from the main upper Mekong and the Nam Khan River were significantly differentiated, but on a time scale inferred to be short (i.e. by genetic drift, not sufficient for evolution of new microsatellite alleles). The Mekong stock of C. molitorella was strongly differentiated from those from the Red and Pearl Rivers, inferred to be on an evolutionary time scale. Finer-scale sampling is warranted to further improve the understanding of genetic interactions among fish from the Mekong and its tributaries. Detailed studies on the ecology of C. molitorella (e.g. migration pathways and preferred spawning habitats) would provide useful information to explain the patterns of genetic structure detected here, and deepen insights about evolutionary distinctiveness of the population units.

Impact of fermented mulberry leaf and fish offal in diet formulation of Indian major carp (Labeo rohita)

Large quantities of fish offal and mulberry leaf are generated globally. The present study aimed to understand their potential utilization in aqua diet formulation, after proper fermentation, as raw materials to replace fish meal in Indian major carp (Labeo rohita) compounded diet. Fish offal meal (FOM) and mulberry leaf meal (MLM) were used in a 2 × 3 factorial design, to evaluate (i) two different fermented mixtures with the inclusion of both FOM and MLM or only MLM and (ii) to replace three different level of dietary fishmeal: 50, 75 or 80 %. An indoor trial, to evaluate diet intake and digestibility and an outdoor trial to evaluate growth performances were impended in Indian major carp fingerlings. The results showed that FOM and MLM are promising raw materials that can be successfully used in the formulation of diet for the Indian major carp. Specifically, the addition of a proper amount of MLM in the fermentation of FOM produced a fermented mixture that could successfully replace up to 80 % of FM in the diet formulation.

Weaning of Australian shortfin glass eels (Anguilla Australis): a comparison on the effectiveness of four types of fish roe

Eel culture is solely dependent on wild seed stock, caught in estuaries during the freshwater migratory phase as glass eels. The methods used for weaning glass eels are very variable, and range from the use of live zooplankton to fish roe to fines of commercial fish feeds. The present experiments were conducted on glass eels of the Australian shortfin eel, when the effectiveness of four types of readily available fish roe (European carp, mirror dory, orange roughy and warehou) were evaluated over a 42-day period, in the laboratory.

After 28 days the eels did not show an interest in orange roughy and mirror dory roe, and these two treatments were discontinued to avoid mortality. In all treatments there was a decrease in mean weight during this period, but the survival was over 99%. In the 28th to 42nd day period the mean weight and specific growth rate of glass eels reared on European carp and warehou roe increased, but the differences between these two treatments were not significant.

The physical features of the roe and the oocytes thereof, the proximate composition, amino acid and fatty acid composition indicated major differences amongst the roe types, particularly with regard to the amount of n−6 polyunsaturated fatty acids (PUFA) and the ratio of n−3 to n−6. European carp and warehou roe (and oocytes) had a significantly higher arachidonic acid (AA-20:4n−6; over 60% of PUFA) content and a considerably lower n−3 to n−6 ratio (n−3 to n−6 ratio being 1.32, 5.92, 3.77 and 2.67 for roe types, and 1.25, 4.83, 2.91 and 2.42 for oocytes, of European carp, mirror dory, orange roughy and warehou, respectively), than in the other two roe types. The fatty acid profiles of European carp and warehou roe were similar to that of metamorphosing glass eels.

An evaluation of the suitability of selected waste products in feeds for three fish species

Five types of aquatic food industry waste products (carp offal, carp roe, fish frames, trout offal and surimi processing waste) together with fish meal were evaluated for their suitability as potential fish meal replacements, partially or wholly, in diets for three species (rainbow trout, Murray cod and shortfin eel) cultured in Australia, using a number of criteria.

The proximate composition of the ingredients on a dry matter basis including protein content, lipid and ash, varied considerably. The essential amino acid (EAA) contents of the waste products and fish meal decreased in the order: carp roe > fish meal > carp offal > 'surimi' processing waste > fish frames > trout offal. The results of cluster analysis of A/E ratios of waste products and fish whole body fell within three clusters. The EAAI of whole body tissue of Murray cod, rainbow trout and Australian shortfin eel however, were closest to fish meal, followed by fish frame waste and/or 'surimi' waste. The results on A/E ratios and EAAI did not conform to the raw data on TAA and EAA. Therefore, the study emphasizes the need to have a multi-prong approach to determine the suitability of ingredients for incorporation into fish feeds.

Fisheries and cage culture of three reservoirs in west Java, Indonesia; a case study of ambitious development and resulting interactions

The interactions between cage culture and wild fishery activities in three Indonesian reservoirs, Saguling, Cirata and Jatiluhur, of the greater Ciratum watershed, West Java, were evaluated using historical data and interviews with cage culture operators. In all three reservoirs, cage culture of common carp, Cyprinus carpio L., and later of common carp and Nile tilapia, Oreochromis niloticus (L.), were encouraged as an alternative livelihood for persons displaced by the impoundment. Currently, a two-net culture system, locally known as 'lapis dua', in which in the inner cage (7 × 7 × 3 m) is used for common carp culture and the outer cage (7 × 7 × 5/7 m) is stocked with Nile tilapia, is practised. On average each cage is stocked with  approximately 100 kg fingerlings each of common carp and Nile tilapia. The numbers of cages and production of cultured fish has increased in the reservoirs, but total and per cage production began to decline from about 1995 in Saguling from 2200 kg cage−1 in 1989 to <500 kg cage−1 in 2002, and in Cirata from a peak of approximately 2300 kg cage−1 in 1995 to approximately 400 kg cage−1 in 2002. In Jatiluhur, which has a considerably lower cage density, total fish production and production per cage has increased since 2000, and currently is approximately 4000 kg cage−1, close to production in the early years of cage culture activities. The cage culture operations also resulted in substantial nutrient loading, estimated at 3.2, 15.2 and 3.1 t of nitrogen and 134, 636 and 128 kg of phosphorous per year in the maximum years of production for Saguling, Cirata and Jatiluhur reservoirs, respectively. In later years, when cage culture production was high, fish kills occurred in the cages, and in Jatiluhur reservoir coincided with a dramatic decline in wild fishery catches. An attempt is made to determine the maximum number of cages for each of the reservoirs that will bring long-term sustainability of cage culture operations and the wild fisheries in the three reservoirs.

An evaluation of the role and impacts of alien finfish in Asian inland aquaculture

Asia dominates global aquaculture production accounting for over 80% of the total and the mainstay in Asian aquaculture is finfish. Over the years, Asia has experienced a number of inter-continental and intra-continental transfers/introductions/translocation of finfish species, between nations and watersheds, beyond their natural range of distribution, primarily for aquaculture development. In this article all such species are referred to as alien species. An attempt is made to evaluate the importance of the production of alien species in selected Asian nations, using statistics of the Food and Agriculture Organization. Also, negative effects, if any, based on literature surveys, of alien species in relation to displacement of indigenous species, and on biodiversity and/or genetic diversity together with associated pathogen transfers are evaluated. The major alien species, based on their significance to Asian inland aquaculture considered, are the tilapias, catfish, Chinese and Indian major carps and common carp. It is estimated that currently alien species account for nearly 12% of the cultured finfish production (2.6 million tonnes) in Asia, valued at US$ 2.59 billion, and the contribution exceeds 40% when Asian countries excluding China are taken into consideration. Inland finfish aquaculture in some Asian nations, such as Indonesia and the Philippines, is predominated by alien species, and in some others, e.g. Bangladesh and India, the contribution from alien species has been increasing steadily. It is suggested that overall alien finfish species have done little ecological harm to native flora and fauna. However, in the wake of increasing anthropogenic development taking place in watersheds the resulting environments are often made unconducive to indigenous species but not to some alien species, thereby potentially and indirectly making the latter invasive.

The culture-based fisheries in small, farmer-managed reservoirs in two provinces of northern Vietnam: an evaluation based on three production cycles

In this paper the results of a study conducted on the culture-based fisheries in small (ranging from 2 to 160 ha), farmer-managed reservoirs in YenBai and ThaiNguyen Provinces in the northern highland region of Vietnam, for the production cycles of 1997/98, 98/99 and 99/00 are presented. The small reservoirs are leased to small farmers by the provincial authorities for fishery activities, and all lessees adopt culture-based fisheries when fingerlings of grass carp (Ctenopharyngodon idella), silver carp (Hypophthalmichthys molitrix), bighead carp (Aristichthys nobilis), common carp (Cyprinus carpio) and mrigal (Cirrihinus mrigala) are stocked between March and mid-April each year and harvested, using large seine nets, after approximately 11-12 months. The mean yields from reservoirs in YenBai and ThaiNguyen Provinces in 97/98, 98/99 and 99/00 production cycles were 251, 332 and 253, and 331, 372 and 210 kg ha⁻¹ respectively. There were major differences in the fish productivity in the reservoirs in the two Provinces, and in a reservoir between culture cycles. The stocking strategies appeared to be rather ad hoc, being determined by the availability of seed stock and the financial status of the lessees. Accordingly, there was no apparent consistent trend in the improvement of yields from the culture-based fishery practice throughout the growth cycles. The fish yields in reservoirs in each Province were significantly related to reservoir area (exponentially) and to mean weight of stocked fish and conductivity (logarithmically). Of the stocked fish, the highest returns were obtained with mrigal and bighead carp, which collectively contributed > 50% to the harvest. The return from common carp was the lowest. The mean growth rate of grass carp (2.7 g day⁻¹), followed by bighead carp (2.0 g day⁻¹) was the highest in reservoirs in YenBai Province, bighead carp (4.0 g day⁻¹) followed by grass carp (3.2 g day⁻¹) was the highest in ThaiNguyen Province. The seed stocked on average accounted for 65% and 48% of the total operating costs in YenBai and ThaiNguyen Provinces, and the mean cost:benefit ratio of the culture-based fishery in the two Provinces was 0.35 and 0.37 respectively. The culture-based fishery on average contributed about 28% to the gross income of a farmer lessee.

Encountering place : tripping to the point

The Nepean Peninsula, a tiny sliver of land at the end of the Mornington Peninsula, Victoria, Australia, has lured humans over eons. Together with the Bellarine Peninsula it forms the gateway to Port Philip Bay at the Heads. It shields the Bay from the tumultuous forces of Bass Strait. Here  generations have been drawn to the seaside, to an inspirational coastal landscape. Today hurtling at 100 km per hour down the Mornington Peninsula Freeway one reaches decision point in less than an hour: the coast road or the inland road? Next looms the junction of the Old Melbourne Road and the Nepean Highway. Another decision: which road will be quicker? Where will the traffic snarl be this time? One is oblivious to the remnant moonah woodland which once covered the land; unaware of the seascape to either side; no longer in tune with the rhythm of the tides. And yet people today still feel that sense of relief and freedom of escape from the metropolis with their first 'sniff of the briny'. Through contemporary accounts and visual material this paper explores the roads that have been travelled to get to the Nepean Peninsula: by land and sea.

Limnology and culture-based fisheries in non-perennial reservoirs in Sri Lanka

This study was carried out to investigate the possibility of using the limnological characteristics of non-perennial reservoirs in Sri Lanka for the future management of culture-based fisheries. Forty-five reservoirs were randomly selected to study their limnology, out of which 32 were stocked with fish fingerlings of Chinese and Indian carps, tilapia and freshwater prawn at stocking densities ranging from 218–4372 fingerlings ha−1. Of these, 23 reservoirs were harvested at the end of the culture period (6–10 months). Thirteen limnological parameters were measured during the water retention period of each of the 45 reservoirs between November 2001 and January 2004. The mean values of the limnological parameters were used to ordinate the reservoirs through principal component analysis. Ordination showed a productivity gradient among reservoirs where Secchi disc depth, total phosphorus, chlorophyll-a, inorganic turbidity and organic turbidity were identified as key factors. The total fish yield of culture-based fisheries was positively correlated to the scores of the first principal component axis. This study reveals that it is possible to classify non-perennial reservoirs in Sri Lanka based on the above limnological parameters in order to develop culture-based fisheries and that they could be applicable in comparable water bodies elsewhere in the tropics.