Acuinuga. Acuicultura y Nutrición de Galicia


20-03-13 |

Prospawn Project

Implementation of natural spawning for marine fish species in culture:

Improving the quality of  offspring and animal welfare

Bringing together a strong assemblage of industrial and academic partners from Holland, Norway, Portugal, Spain and the United Kingdom, this inter-European, collaborative Project fits within the seventh Framework Programme for Research and Technological Development and is co-funded by the European Commission. After three years of coordinated research, a crispier picture on the effects of captivity, current rearing conditions and hatchery practices on spawning success of fish broodstock is starting to emerge.

Out of a wide range of demersal (Atlantic cod, Gadus morhua; black spot sea bream, Pagellus bogaraveo; white sea bream, Diplodus sargus) and flatfish  species tested (Atlantic halibut, Hippoglossus hippoglossus; Senegal sole, Solea senegalensis; European sole, Solea solea; turbot, Scophthalmus maximus),  natural spawning within this project was recorded for cod, European sole and Senegal sole. Appropriate tank design, spawning nests, optimal current speeds and sufficient conditioning play an important part for successful natural spawning, although a general background effect derived from captivity, possibly nutritional, may be affecting the reproductive performance in the species analysed.

Noise and light seem to be amongst the most influential rearing parameters on egg quality. The use of underwater hydrophones in cod broodstock tanks clearly shows a detrimental effect of certain frequency sounds related to routine husbandry practices on fertilization rates; flatfish seem to be more sensitive to low frequency sounds, under 100 Hz. Cod is a noisy species too: broodstock vocalisations or "grunting" were recorded during the spawning season, providing a useful bench mark of the natural communication bandwidths for this species. Experiments conducted with special LED prototypes showed that light intensity and spectrum have a clear impact on broodstock's locomotor activity. This was further investigated by using "actograms", monitoring broodstock behavior with infrared light beams, photocells and special chronobiology software. Understanding behavioural rhythmicity is essential for the implementation of successful spawning protocols; in some species such as the Senegal sole, a very different pattern of behavior was observed between wild and domestic broodstock. Wild individuals are very rhythmic, while domestic fish are totally arrhythmic. All these findings are relevant for the development of optimal farming practices for these species -i.e. feeding, handling, egg collection and fertilization, etc.

When natural spawning does not take place in captivity, it must be induced artificially. Perhaps one of the most relevant achievements of the Prospawn project was the development of a successful artificial protocol for the Senegal sole using reproductive hormones. Although results are still variable and more effective for males than for females, the commercial potential for the cultivation of this species makes this milestone particularly significant. In the soles, as in many other fish species, only a few individuals contribute to the offspring, possibly reflecting social hierarchies. Thus the investigation of the genetic contribution of the broodstock to the offspring was addressed within the context of this project, confirming that the more genetically unrelated that potential parents are, the higher the chances for them to mate. This finding enabled the Consortium to come up with specific recommendations on technical and methodological guidelines for the assessment of mate choice by DNA marker analysis.

The industry needs solutions, and two particularly useful tools seem to have real commercial prospects. One of them is an automated tool for egg quality control. Based on quantifiable image analysis data collected from freshly fertilized ova, the solution developed for the assessment of egg quality during this project provides an invaluable "keep or throw away" indicator, very important in order to optimize resources and time at busy hatcheries during the spawning season. The other is a new holding system, the shallow raceway, which seems to have good potential for species such as the white seabream. The shallow raceway system could facilitate successful natural spawning, egg collection and estimation of fecundity and fertilization rates, not only by saving space, energy and water, but providing breeders with a more accurate overview of the status and reproductive performance of the broodstock.

The marine fishfarming industry in Europe is currently dominated by the culture of a few successfully domesticated species, namely salmonids, sea bass and sea bream.  Farming technology for several alternative species including cod, sole or blackspot sea bream is still under development. The Prospawn Project identified inadequate holding facilities, poor broodstock-keeping practices and suboptimal rearing parameters as the main limiting factors preventing the large-scale production of juveniles for these alternative and other commercially-relevant species. It is essential to overcome the technical limitations conditioning the steady and reliable supply of quality eggs. The uptake by the industry of the practical knowledge derived from this project represents the way forward for the consolidation and expansion of this industry.