There is any number of ways to grow broodfish. Some of them are conducive  bringing out the best in the fish; some of them are not. Nature and nurture have everything to do with making a profit. Growing happy fish also reflects this.

The nature aspect has everything to do with the genetic makeup; what is bred in the bone comes true in the flesh. Conversely, the nurture aspect of brood management brings out the best in your fish and makes them perform optimally. In badly managed breeding programmes, even the best growing conditions serve to grow lousy fish – if that’s what was bred. In bad locations or in cases of poor husbandry, top-shelf fish with great stats will perform as good as grunt fish.

If the job of the geneticist is to evaluate and predict performance in a stock; the job of the broodstock manager is to ensure the potential of that stock is brought to light. So really, it’s the effect of environment on genetic potential. Get one thing clear: the environment does not shape the genetic makeup of the fish, the fish responds to the environment based on a capacity to adapt or compensate. Fish can be selected to perform under adverse or optimal conditions, but it is a difficult task. Better yet is to optimize growing conditions and breed for heritable traits that are more suited to market demands. A salmon that grows in a sewer is a carp.

In both seawater and freshwater broodstock, nutrition and feeding are key components. Fish in cages should be put on a premium broodstock diet no later than 10-12 months prior to normal spawning times. This is most commonly done after the second SW sort or family selection. It also coincides with last harvest of sibs.

Why the long time? It’s the buildup of a good nutritional base prior to building eggs. The spring and summer are critical times for good nutrition as the fish enter gametogenesis. During the spring and early/mid summer, a diet of high quality fish protein, plenty of HUFAs, pigment and vitamins/minerals must be on the menu: no grower diets.

As Niall Bromage, Assistant Director, Institute of Aquaculture at U. of Stirling has shown, feeding regimen is very important. Salmon should be fed a high ration through the period of vitellogenesis and tapered to nothing or very low 4-6 weeks prior to spawning. This feeding regimen optimizes fecundity (egg number) and fish size. This is especially important because under this plan, fecundity is high because fish are large. There is a good correlation (direct relationship) between size and fecundity, but if nutrition and feeding rates are optimal, the larger fish have disproportionably more eggs. Double bonus unless elected to hold the fish during spawning.

For Atlantic salmon, auto feeders are indicated for dispensing feed. Brood salmon tend to have a high metabolism because of the high mass of gonads. These suck up energy and have to be built from scratch. Brood will tend to be most active just before dawn and just after dusk. This is common in the animal kingdom and is known as ‘crepuscular’ activity. In a semi-diurnal tidal area (one large, one small tide change) the tides tend to be about this time as well, so it can coincide with peak flows. This means that feeding times should be largest on the peak flow times to make use of flow and high oxygen. Try setting the feeder for a greater percentage at these times.

After the last performance selection and about the time the broodstock diet is being used, loading density in the brood pen should begin at one-quarter and end at one-half normal rearing density. The normal density of a production pen varies with local conditions and company policy, so the fraction of rearing density is used. As well, nets of larger mesh should be employed to optimize flow. Unfortunately, this makes brood very visible to predators, so use discretion.

The locations of the brood pens are important. Chart the harvest performance of fish on the farm. Chances are the last pens to harvest are those nearest the feed shed or grading table. Human activity tends to make fish grow slower. As well, strong current that billows nets or causes cage disfigurement will cause lower growth and increase mortality. It’s hard to convince someone to put half the fish in the best pen location, but it’s worth it in the long run.

Environmental conditions vary with location and everyone talks about the weather but no one does anything about it. Pick a brood site that is best for fish, not convenience. Parameters such as good flow, cool summer temps, warm winter temps, low lice rate etcetera are rarely found all in one site. If pressed to pick important factors, it would have to be temperature and oxygen.

In freshwater, watch the loading densities and keep oxygen to 100%, but not over. In terms of temp and ppm, keep the water at 10°C or below and always above 6ppm. Hardness helps in terms of osmotic and ionic stress and calcium carbonate such as used in a recirc facility is a good idea. As in SW, oxygen demand (as in activity) is greatest at dawn and dusk and flows/oxygen should be monitored closely at these times.