The effect of seasonal variation on quality


Catching season has an effect on quality and utilisation due to seasonal changes in the condition and chemical composition of fish. During the spawning period, gaping is more noticeable and water content at a maximum. The nutritional status of fish can also be different depending on fishing grounds. The quality of the fish varies with season, for example due to different temperature, sexual maturation and feed supply as can be seen in this Icelandic report (English abstract).

The temperature of the sea has for example an effect on how quickly the optimal storage temperature can be reached in the fish. Sexual maturation has among other factors an effect on texture, chemical composition and body mass where for example newly spawned fish is often very lean. Feed supply can either be too small or large in which case the fish gets fatter in a shorter time resulting in very loose texture. Weather can have an effect on gaping and muscle bruise may result during bad weather due to harsher treatment. Furthermore, number of worms, gaping, bruise and other quality factors can be different between seasons as can be seen in this Icelandic report (English abstract). It can be very difficult and sometimes impossible for the fishery industry to react towards these natural influential factors but those involved in the value chain need to be aware of the effect of seasonal variations on fish quality. In some cases though it's possible to react towards these variations, for example by increased cooling over the summer months (like better pre-cooling, more ice, use tub covers etc.) as can be seen in below.



Sea temperature has an effect on how much ice is needed to cool the catch. Therefore use of ice according to season and fishing ground. Common sea temperature during summer at the South-coast of Iceland is 8-12 °C and then up to 15 kg ice is needed (ca. 3 buckets) to cool each 100 kg of fish down to 0 °C. If liquid ice (mixture of ice and seawater) is used, about 16 kg of ice and 15 L seawater is needed to achieve similar cooling. Additionally, extra ice is needed to maintain the cooling temperature.

Here are equations to calculate ice requirement to cool fish down to 0°C and to maintain 0°C.



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