Mytilus galloprovincialis Lamarck: influence of collection month and culture area on morphometric and quality characteristics

Abstract

Aquaculture is a very ancient activity: carp breeding appears to date back to 2500 BC. Mollusc culture is an important production activity carried out in marine or lake zones with suitable microbiological, chemical and physical water characteristics and abundant plankton, in which mussels have a prominent role. The study was directed at evaluating the morphometric and quality characteristics of commercial Mytilus galloprovincialis from two culture areas in the mid Adriatic: Ancona (natural and artificial open water cultured area) and Bellaria (only artificial cultured area). Seven samples per area, each weighing 3kg, were collected from June to December. Specimens were examined for size (length, width, thickness, maximum longitudinal and transverse circumference) and weight (total, flesh, shell). The flesh was analyzed to determine its content in moisture, protein, fat, ash, fatty acids and crude energy. ANOVA and χ2 test were applied. Specimens were divided into three length categories (<5cm; 5-7cm; >7cm). The mean values measured in the whole sample (n=2300) were: length 5.83±0.86 cm, width 2.93±0.39cm, transverse circumference 7.72±1.02cm, total weight 14.22±6.83g, flesh 4.79±2.36g. Given a variability of 14-15% of the morphometric data, the variation coefficient of weight parameters is around 50%. With reference to the commercial categories (5-7 and >7cm), significant differences were found for all months except August and November, most consistently for the two classes >5 in the samples from Bellaria compared with Ancona, where from June to October cultured as well as naturally growing mussels are collected. As regards quality, there were no differences related to the area of collection, whereas variations in dry matter, which tended to diminish, and in protein, which increased, were noted from June to December. In conclusion, the characteristics of mussels are strongly influenced by the culture area and by environmental factors (month of collection). The better characteristics of the product collected in the summer confirm a greater metabolic activity of the molluscs at this time of year and its favourable influence on the flesh chemical composition.