Genetic improvement and effective dissemination: keys to prosperous and sustainable aquaculture industries

There is an increasing demand for fish in the world due to a growing population, better economic situation in some sectors, and greater awareness of health issues in relation to food. Since capture fisheries have stagnated, fish farming has become a very fast growing food production system. In this presentation, the author gives an overview of the technologies that are available for genetic improvement of fish, and briefly discuss their merit in the context of a sustainable development. He also discusses the essential prerequisites for effective dissemination of improved stock to farmers. It is concluded that genetic improvement programs based on selective breeding can substantially contribute to sustainable fish production systems. Furthermore, if such genetic improvement programs are followed up with effective dissemination strategies, they can result in a positive impact on farmers' incomes.

Culturable fish seeds in Nigerian waters: A research survey (1978-1985)

The desired species identified in this survey include mullets, catfishes, fast growing fish predators, species for control of weeds and grass it, ponds, cichlids and shrimps. Five coastal states: Lagos, Ondo, Bendel, Rivers, and Cross River were covered in the studies. Investigations were also carried into the major rivers and their tributaries. A combination of the estimation methods of Le Cren, (1962) and Pitcher and Mac Donald (1973) was employed in the analysis of data. From the detailed data collected from (1978-1985), the survey indicated that about 100 million fish seeds can be collected annually from Nigerian waters using appropriate gear-seine nets, cast nets, and fish traps. Of this number, 60% is available along the coastal belt of the country while 40% is in the major rivers, their tributaries and swamps. At the present level of fish culture development in Nigeria, this is more than enough, even after allowing for 50% mortality due to handling and transportation stress

Prey preference of lingcod (Ophiodon elongatus), a top marine predator: implications for ecosystem-based fisheries management

Many highly exploited ecosystems are managed on the basis of single-species demographic information. This management approach can exacerbate tensions among stakeholders with competing interests who in turn rely on data with notoriously high variance. In this case study, an application of diet and dive survey data was used to describe the prey preference of lingcod (Ophiodon elongatus) in a predictive framework on nearshore reefs off Oregon. The lingcod is a large, fast-growing generalist predator of invertebrates and fishes. In response to concerns that lingcod may significantly reduce diminished populations of rockfishes (Sebastes spp.), the diets of 375 lingcod on nearshore reefs along the Oregon Coast were compared with estimates of relative prey availability from dive surveys. In contrast to the transient pelagic fishes that comprised 46% of lingcod diet by number, rockfishes comprised at most 4.7% of prey items. Rockfishes were the most abundant potential prey observed in dive surveys, yet they were the least preferred. Ecosystem-based fisheries management (EBFM) requires information about primary trophic relationships, as well as relative abundance and distribution data for multiple species. This study shows that, at a minimum, predation relative to prey availability must be considered before predator effects can be understood in a management context.

Comparison of life history parameters for landed and discarded fish captured off the southeastern United States

Commercial fisheries that are managed with minimum size limits protect small fish of all ages and may affect size-selective mortality by the differential removal of fast growing fish. This differential removal may decrease the average size at age, maturation, or sexual transition of the exploited population. When fishery-independent data are not available, a comparison of life history parameters of landed with those of discarded fish (by regulation) will indicate if differential mortality is occurring with the capture of young but large fish (fast growing phenotypes). Indications of this differential size-selective mortality would include the following: the discarded portion of the target fish would have similar age ranges but smaller sizes at age, maturation, and sexual transition as that of landed fish. We examined three species with minimum size limits but different exploitation histories. The known heavily exploited species (Rhomboplites aurorubens [vermilion snapper] and Pagrus pagrus [red porgy]) show signs of this differential mortality. Their landed catch includes many young, large fish, whereas discarded fish had a similar age range and mean ages but smaller sizes at age than the landed fish. The unknown exploited species, Mycteroperca phenax (scamp), showed no signs of differential mortality due to size-selective fishing. Landed catch consisted of old, large fish and discarded scamp had little overlap in age ranges, had significantly different mean ages, and only small differences in size at age when compared to comparable data for landed fish.

Demographics by depth: spatially explicit life-history dynamics of a protogynous reef fish

Distribution and demographics of the hogfish (Lachnolaimus maximus) were investigated by using a combined approach of in situ observations and life history analyses. Presence, density, size, age, and size and age at sex change all varied with depth in the eastern Gulf of Mexico. Hogfish (64–774 mm fork length and 0–19 years old) were observed year-round and were most common over complex, natural hard bottom habitat. As depth increased, the presence and density of hogfish decreased, but mean size and age increased. Size at age was smaller nearshore (<30 m). Length and age at sex change of nearshore hogfish were half those of offshore hogfish and were coincident with the minimum legal size limit. Fishing pressure is presumably greater nearshore and presents a confounding source of increased mortality; however, a strong red tide occurred the year before this study began and likely also affected nearshore demographics. Nevertheless, these data indicate ontogenetic migration and escapement of fast-growing fish to offshore habitat, both of which should reduce the likelihood of fishing-induced evolution. Data regarding the hogfish fishery are limited and regionally dependent, which has confounded previous stock assessments; however, the spatially explicit vital rates reported herein can be applied to future monitoring efforts.

Increases in the relative abundance of mid-trophic level fishes concurrent with declines in apex predators in the subtropical North Pacific, 1996–2006

Catch rates for the 13 most abundant species caught in the deep-set Hawaii-based longline fishery over the past decade (1996–2006) provide evidence of a change among the top North Pacific subtropical predators. Catch rates for apex predators such as blue shark (Prionace glauca), bigeye (Thunnus obesus) and albacore (Thunnus alalunga) tunas, shortbill spearfish (Tetrapturus angustirostris), and striped marlin (Tetrapturus audax) declined by 3% to 9% per year and catch rates for four midtrophic species, mahimahi (Coryphaena hippurus), sickle pomfret (Taractichthys steindachneri), escolar (Lepidocybium flavobrunneum), and snake mackerel (Gempylus serpens), increased by 6% to 18% per year. The mean trophic level of the catch for these 13 species declined 5%, from 3.85 to 3.66. A shift in the ecosystem to an increase in midtrophic-level, fast-growing and short-lived species is indicated by the decline in apex predators in the catch (from 70% to 40%) and the increase in species with production to biomass values of 1.0 or larger in the catch (from 20% to 40%). This altered ecosystem may exhibit more temporal variation in response to climate variability.

The quest for temperature records in California free of urban heat island effects [abstract, figures, and tables]

EXTRACT (SEE PDF FOR FULL ABSTRACT): The data of this paper differ from the Jones and Bradley papers [of 1982-1986] in that it represents an attempt to select thermal pollution free records rather than to include all available records. The specific long-term trends that this paper is trying to avoid are those illustrated by the heat islands of fast growing urban locations. One other major difference in this paper is that all of the records reported of this study are complete for the entire study period.

Age and growth of the bastard grunt (Pomadasys incisus: Haemulidae) inhabiting the Canarian archipelago, Northwest Africa

The bastard grunt (Pomadasys incisus) is one of the most abundant coastal demersal fishes inhabiting the Canary Islands. Age and growth were studied from samples collected between October 2000 and September 2001. Growth analysis revealed that this species is a fast growing and moderately short-lived species (ages up to seven years recorded). Length-at-age was described by the von Bertalanffy growth model (L∞=309.58 mm; k=0.220/year; t0=–1.865 year), the Schnute growth model (y1=126.66 mm; y2=293.50 mm; a=–0.426; b= 5.963), and the seasonalized von Bertalanffy growth model (L∞=309.93 mm; k=0.218/ year; t0= –1.896 year; C=0.555; ts=0.652). Individuals grow quickly in their first year, attaining approximately 60% of their maximum length; after the first year, their growth rate drops rapidly as energy is probably diverted to reproduction. The parameters of the von Bertalanffy weight growth curve were W∞=788.22 mm; k=0.1567/year; t0= –1.984 year. Fish total length and otolith radius were closely correlated, r2=0.912. A power relationship was estimated between the total length and the otolith radius (a=49.93; ν=0.851). A year’s growth was represented by an opaque and hyaline (translucent) zone—an annulus. Backcalculated lengths were similar to those predicted by the growth models. Growth parameters estimated from the backcalculated sizes at age were L∞=315.23 mm; k=0.217/year; and t0= –1.73 year.

Strategy of fish seed production in India

In tropical countries like India, climatic conditions vary in different parts, as a result the breeding of fast growing species such as Catla and silver carps poses considerable problems due to erratic or late monsoon or prolonged dry spell. Hence it is not possible to meet the fish seed requirement of the country. Therefore: to meet the future requirement and to over-come the environmental conditions a Modern carp Hatchery CIFE D-81 was designed. The system provides optimum temperature, silt free clean, cool, highly oxygenated water, low current and continuous removal of metabolites. It has been successfully demonstrated at Rawatbhata (Rajasthan), Badkhal (Haryana), Badbhada (M.P), Guntur and East Godavari District (A.P). Recently a Modern Carp Hatchery was installed in a semi-arid zone, Damdama (Haryana), during 1984, where it has produced record 1.88 crores of fish seed and worked successfully.

A comparative note on the modus operandii of reservoir development in Republic of China and India

Principles adopted by China for the development of reservoir fisheries are discussed. Production of some of reservoirs of China with that of India is compared. The reasons for obtaining higher production in China have been recognised as: emphasis on utilization of all resources for food production; direct feeding; use of selected varieties of fast growing carps; keeping 15 pigs per hectare of water area for application of pig void and application of manure; production of fingerlings at the reservoir sites enclaving coves and bays; grading and removing obstructions from bottom; rational harvesting and stocking and improvement of reservoir shore areas as a whole. Some of these measures which could be implemented in Indian conditions are briefly described.

Studies on paddy-cum-fish culture under different land situations

Paddy fields can be broadly classified on the basis of land situations viz. Upland - Shallow water (10-30 cm), Medium land-medium deepwater (30-100 cm) and Low land-deepwater (above 100 cm). Three major systems of paddy-cum-fish culture, viz. (A) high yielding paddy varieties (H.Y.V) and air-breathing fish under Upland, (B) H.Y.V./local paddy and Tilapia/common carp under Medium land and (C) deepwater paddy and major Indian carps under Low land situations have been successfully investigated in the farmers' fields and at the Research Stations (1982-92). Effects of low-cost artificial feeding on growth, yield and management practices of different types of fish showed a considerable increase of rice and fish yields and a decrease in insect-pest incidence. Under Upland situation, short duration H.Y.V. in combination with fast-growing air breathing fish was studied thrice a year (summer, winter & autumn seasons). Combined rice and fish culture produced highest yields in all the seasons than in the control.

Investigation of polymorphism by PCR-RFLP method in Cobia fish Rachycentron canadum in the Persian Gulf and Oman Sea

Cobia is a native fish species in Iranian waters in the Persian Gulf and Sea of Oman and has a good internal and foreign market. This fish is a fast growing species and for this reason Iranian Fisheries is considering to go for it culture practices. To go for any utilization such as fishing from wild stocks or culture activities, needs a better understanding of its peculiarities and genetic characteristics of its natural resources. Therefore, this project was discribed and conducted. In this investigation, cuts 2 or 3 cm of fin tissue of  specimen of Cobia obtained from Sistan and Bluchestan, Hormozgan, Bushehr and Khuzestan water provinces, were collected. DNA was extracted by Phenol-chlorophorm method and produced PCR product in length of 1060 and 1450 base pair of two mitochondrial genes COI and NADH2. Using 13 cutting enzymes (4 enzymes were subscriber for both of genes), 205 base pair (from 2510 base pair, equal with %3.8 from gene regains) were directly investigated. But binding patterns of enzymatic digestion of PCR products of both COI and ND genes from electrophoresis were monomorph in all samples and no polymorphism was observed. This may be attributed to the unsuitable choice of COI and ND2 genes for showing of intra specific divergence. But in general non-existence of genetic diversity or noticeable decrease of that among individuals has been reported in regions were fish migration exist and they can freely move between two regions. Therefore, non-observation of polymorphism in the study area might be the case and indicates represents the area. On the other hand, some scientists believe that the distributions of populations in different regions are greatly affected by environmental and physical and ecological factors. Althoug Cobia is a migratory fish, but with regard to the fact that the environmental conditions are different (specially temperature and salinity) between east and west of Persian Gulf and Oman sea, there is a possibility that different genetic groups of this species exist in the regions. Of course It is clear that using more samples and enzymes from other genetically regions could produce better results. Since none of the two investigated genes didn’t show genetic divergence or polymorphism amongst the individuals of one region or between different regions, therefore, statistic analysis for estimating of haplotype diversity or nucleotide diversity and drawing of relationship tree among individuals using available softwares was not possible.

Agiis: a bivalve cultivated as live shrimp feed

Live 'agiis' have been proven to be a good feed for shrimp for the past ten years by polyculture fish farmers in the province of Capiz, in the island of Panay, west central Philippines. A brief account is given of culture and feeding operations. Its cultivation period is short and seeds are readily available. It can reduce dependence on trash fish which is now getting to be scarce; it also seems much cheaper. Perhaps this fast-growing tiny bivalve can be scientifically investigated by students of aquaculture as feed for other commercial aquaculture species. Its scientific identification can be a good start.

The exploitation of small pelagic fishes of the great lakes of Africa with reference to the mukene (Rastrineobola argentea) fishery of the northern waters of Lake Victoria

Small pelagic fish species have ultimately become important on most of the Great Lakes of Africa, especially after the depletion of the larger, initially preferred fish species. In Lake Victoria, the small pelagic cyprinid Rastrineobola argentea is now the only abundant native species supporting a fast growing light fishery. In Pilkington Bay, off Lingira Island the artisanal light fishery is well established and in the last two years this bay has witnessed a sharp increase in the fishing effort. This has been followed by a modification of fishing method and a reduction in the mesh size of nets used. R. argentea now caught from this bay consist of mainly juveniles and this could result into localized recruitment overfishing. Drawing examples from what is happening to the fishery in Pilkington Bay, it is necessary to carry out research on the stocks, gear and suitable fishing crafts before light fishing spreads to most parts of the lake.

Fast fingerling production: nursing spawn in ponds

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