Qualitative and quantitative models relating otolith zone deposition to growth and condition in sexually mature male and female capelin (Mallotus villosus)

Abstract

Correspondence analysis (CA) is used to examine the relationship between months, between selected body components/organs and between months and components/organs for male and female capelin from 12 to 37 months of age in Balsfijorden, northern Norway (69°21′N:19°06′E). The CA profiles have been used to quantify condition with regard to age and season. The major features determining the condition of fish depositing hyaline or opaque otolith zones are itemized using CA, and the data modelled by Multiple Regression (MR) using a cosine curve incorporating the chief mass variables with linear age-dependency. The highest proportion of fish having outer opaque zones are found from ca. June to October, whilst the highest proportion with exterior hyaline zones are found from ca. December to May. There is a clear annual cycle in the deposition of opaque and hyaline otolith zones in both sexes, but there is a significant difference in phase of ca. 12 days between the sexes. There is a significant trend for decreasing proportions of fish having outermost opaque otolith zones with increasing age; this trend is similar in both sexes. The mean level and amplitude of the cycles are similar in both sexes. On the other hand, CA shows a 12-month cycle of storage and utilization of body materials with obvious differences between sexes. In the female protein in the fillet plays a more dominant role than lipid in the fillet in accounting for anabolic and catabolic variations in mass, whereas in the male the opposite is true. Sexual maturation is negatively correlated with fillet (somatic) growth. Variations in stomach weight (with contents) and otolith zone deposition are not significantly correlated. Nevertheless, in both sexes there is a clear positive correlation between stomach weight and liver protein and lipid implying an association between stomach weight and feeding activity. In females, however, maximum liver condition is more positively correlated with exponential ovarian growth, probably through mobilization of lipoproteins for eggs. Qualitative (CA) and quantitative (MR) models have related changes in growth and condition to the type of otolith zone deposited. The fillet of capelin is the major somatic growth site. As CA indicates a negative correlation between fillet reserves and gonad maturation, and the best MR models describing the cycle of otolith zone deposition in males and females (accounting for 93% and 70% respectively of the variation) underlined and quantified the interplay between somatic and gonad growth, it is implicit that the energy balance of the fish will be an important determinant of otolith zone deposition in sexually maturing and mature capelin.