A model to estimate the annual production of roes (avgotaracho) of flathead mullet (Mugil cephalus) based on the spawning migration of species

The seaward spawning migration of the flathead mullet (Mugil cephalus L, Pisces: Mugilidae) from daily landings caught by fish traps in the Paleopotamos lagoon (part of Messolonghi-Etoliko lagoon complex) and their relationship with the annual production of avgotaracho (dried, salted and waxed ripe ovaries) were studied. The spawning migration of flathead mullet takes place from August to October. During this period in 1994, 2808 specimens of flathead mullet with mean weight of 809.1 ± 338.0 g were caught. The overall sex ratio of the mature individuals was 1:1, the proportion of the females from which suitable ovaries were derived for avgotaracho manufactured on the total individuals caught at the same period was 34.4% and the mean weight of avgotaracho was 165.2 ± 39.4 g. A model was developed and the annual production of avgotaracho is estimated at about 7% of the landings of flathead mullet caught during their spawning migration period. A simulation showed that the error estimation of avgotaracho provided from the quantity of the available landings of the flathead was about 48.17% of the annual avgotaracho production. Assuming that the spawning migrations as well as the gonad maturity of flathead mullet between the sub-areas of the complex are synchronous, the model can be used to forecast of the annual avgotaracho production. The model's assumptions are discussed.