aquaculture

Fisheries Global Information System (part of the FAO) have produced a fact sheet on farming crucian carp (Carassius carassius).

Global production of farmed crucian carp was only 2977 tonnes in 1950 but had reached 1 702 778 tonnes by 2002, an increase of more than 572 times in 52 years. Crucian carp ranks 6th among all cultured freshwater fish globally and contributed 7.4% of the world freshwater aquaculture production in 2002. Most of the expansion was in China where the average annual growth rate between 1993 and 2002 was 21.6%/yr. Expansion in other countries has been much slower, due to the relatively small size and large number of fine inter-muscular bones, which make the fish less acceptable to consumers in many countries. Taiwan Province of China is another important producer; its annual production was maintained above 3000 tonnes/yr in the early 1980s (with a peak of 3764 tonnes in 1981) but has fluctuated wildly; from 1997-2002 it was in the 2000-2500 tonnes/yr range. Production in Japan, which has a long history of cultivating this species, is much less now than it was in the late 1960s.

The total value of cultured crucian carp production globally was US$ 1.20 billion in 2002, representing an APR of 15.4/yr. This apparently slower rate of expansion in value is mainly due to the devaluation of Chinese currency against the US dollar.

Mat Couchman’s honours project for his degree from the University of Plymouth was an investigation into the feeding interactions among crucian and common carp species within a small reservoir within the university grounds.

The full manuscript (10,000 words) is available from Mat by e-mail request.

Abstract:

The food choice of crucian carp (Carassius carassius) in Drakes reservoir and the influences upon on this by the aquatic environment were investigated.

Thirty-five fish stomachs were observed and it was found that the feeding preference of the crucians revolved around chironomid larvae (Chironomus), small bodied pelagic cladocera (C. ovalis), benthic cladocera (A. affinis) and one species of ostracoda (Cypridopsis). The chironomid larvae and benthic cladocera became more important as the fish increased in length. Rotifers and phytoplankton were not an important part of the diet; Arcella were utilised, but in unknown proportions.

It is suggested that heavy macrophyte growth was the main organism responsible for many interactions and influences upon the fishes’ diet and species diversity in the reservoir.

This population of crucian carp is omnivorous, relying upon more benthic organisms as they increase in length. Stunted growth suggests that intraspecific competition is prevalent in the reservoir. Interspecific competition with common carp (Cyprinus carpio) is suggested. It is believed the crucian carp have reverted to a more cladoceran-based diet to combat this competition with the common carp; this indicates a predominately benthic niche overlap between species.

Paul Adler examines young lettuce seedlings which are grown for about 3 weeks in a separate hydroponic system before they are set in the “conveyor production system” to remove nutrients from the rainbow trout effluent. (Photo by Keith Weller, USDA-ARS).

Adler, P.R. 1998. Phytoremediation of aquaculture effluents. Aquaponics J. 4(4):10-15. From the abstract:

The study is on an integrated system for rainbow trout production, effluent treatment and production of lettuce. The objective was to reuse water by removal of the nutrients in a vegetable product. The microscreen filter removes about 80% of the P excreted by the fish with the biosolids, leaving about 20% of the P in the effluent. A mass balance of system nutrients was conducted and it was determined that it takes 7.5 – 10 heads of lettuce to remove the P excreted in the effluent by the production of 1 pound of trout or 13 – 18 lettuce heads for each kg of feed consumed. Greenhouse studies demonstrated that by using the conveyor production strategy (CPS), phosphorus could be removed to <0.01 mg/L by lettuce without an apparent reduction in production or quality.

Conventional thinking regarding the use of food crops to clean aquaculture effluents has been that plants cannot remove nutrients in water to low levels without a reduction in productivity and quality. If water is distributed in a horizontal plug-flow pattern, all nutrients will be luxury consumed at the inlet, making nutrients limiting at the outlet and significant greenhouse space will be dedicated to growing plants that have no market value.

Because greenhouse space is expensive, productivity is critical for a profitable operation. A unique production system for lettuce, called the conveyor production strategy (CPS), was developed using thin-film technology for plant production in dilute aquaculture effluents. With the CPS, young plants are positioned near the solution inlet and are moved progressively, like along a conveyor belt, towards the outlet as they grow. Luxury consumption by lettuce (Lactuca sativa L.cv. Ostinata) enabled them to store P in their tissues early in their growth cycle for use later as water P levels decreased and influx could no longer meet current demands.

An economic evaluation of Pacu – Piaractus mesopotamicus juvenile production in different rearing systems is available for free download.

In this study, the authors, Rosangela Kiyoko Jomori, Dalton José Carneiro, Maria Inez Espagnoli Geraldo Martins and Maria Célia Portella, evaluated the costs and gross income related to the production of juvenile pacu, Piaractus mesopotamicus.

The larviculture technique for the production of juveniles usually employed in Brazil is the semi-intensive system, which consists in stocking the larvae in fertilized ponds from the time when exogenous feeding begins until the juvenile stage (Senhorini et al., 1991). Nevertheless, the survival rates obtained with this system are usually low, making large-scale production more difficult.

When rearing common carp (Cyprinus carpio), tambaqui (Colossoma macropomum), and pacu (Piaractus mesopotamicus) larvae in fertilized ponds, Chabalin et al. (1989) obtained survival rates around 35%, 30%, and 20%, respectively, at the end of juvenile rearing. The authors suggested that the pacu juvenile rearing technique needed to be improved.

Perch are attracting increasing interest as a species suitable for aquaculture. Wheeler (1996) reported perch reaching 500mm (20″) and 4.75 kg (10.5 pounds) in Europe, but Lake (1971) recorded a perch weighing 10.4 kg (22.9 pounds) in Australia.

Recent Danish research show that perch has a good farming potential. It is suggested by the Danish Institute for Fisheries Research (DFU) that perch could complement rainbow trout and eel, the traditional farmed species in Denmark. The Danish Institute for Fisheries Research (DFU) is also available in English.

According to yellow perch research published by Fisheries Technology Associates, Inc; yellow perch is capable of yielding 45% edible flesh, more than tilapia or catfish, and the tasty flesh freezes and stores well. Perch survive in a wide variety of water conditions, temperatures and salinities.