Studies on the reproduction and culture of the roach (Rutilus rutilus)

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Worthington, A.D., 1983. Studies on the reproduction and culture of the roach (Rutilus rutilus). PhD, Nottingham Trent University.

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Abstract

Studies on the reproduction and culture of the roach (Rutilus rutilus) By A D Worthington Aspects of roach culture have been investigated with the aim of providing information applicable to the commercial farming of this species.

Laboratory-maintained adult roach captured from the wild developed a fatal bacterial disease thought to be caused by host stress. This was investigated by determining cortisol titres from serial plasma samples taken from fish maintained in various environments. Plasma cortisol rose and remained elevated for over 60 days from capture in survivors. The cortisol stress-response to such treatments is probably sufficient, to induce manifestation of the disease.

The manipulation of reproduction is facilitated by knowledge of natural cycles. Annual patterns were established: in females for gonosomatic index (GSI), hepatosomatic index (HSI) and plasma calcium as an index of vitellogenesis; and in males for GSI and plasma cortisol.

Induced spawning of roach with carp pituitary extract (CPE) and the antioestrogens tamoxifen and clomiphene citrate was studied. The effectiveness of CPE was confirmed. Tamoxifen and, to a lesser extent, clomiphene were also effective.

To extend the growing season of fry, methods of early spawning by hormonal and environmental manipulations were investigated, Salmon GtH, clomiphene and tamoxifen treatments did not accelerate gametogenesis. However, the early provision of spring-like light and temperature regimes advanced spawning by 13 to 16 weeks compared with wild fish.

The rearing of larvae in manured ponds enclosed by greenhouses was studied as an alternative technique to intensive hatchery methods. Roach larvae grew very rapidly in greenhouse ponds, with a high percentage surviving to 50 mm.

The production of fry stocked as larvae at 10, 15, 20 and 30 in outside ponds was examined. Rapid growth, high survival and yield ware observed at 20 .

The results were discussed and integrated to form a series of recommended procedures for the culture of roach.