Abstract

Barbados has a small, unmanaged, artisanal conch fishery with a high proportion of immature animals in the catch, and a very low overall abundance of adult conch. As such, protection of the remaining spawning stock is critical to ensure the maintenance of the populations' reproductive capacity. However, nothing is known of the reproductive characteristics of queen conch in Barbados. To address this knowledge gap, we investigated reproductive seasonality and size at sexual maturity of the local conch population. Conch were sampled every month for a full year (September 2009 - August 2010) from the catch of a commercial fisher. The shell lip thickness was measured, and the entire visceral mass was removed and taken to the laboratory for further sectioning. A 1 cm2 cross section of tissue was cut from the mid-length of the gonad and digestive gland and placed in 10% buffered formaldehyde and sea water for a maximum of two weeks. The gonad tissue was processed using histological methods of dehydration, clearing, and embedding adapted from the techniques used by Avila-Poveda et al. (2005, 2006) and L. Frenkiel, Laboratoire de Biologie Animale, Universite Antille-Guyane, Guadeloupe (Personal communication). A 6 ?m thick ribbon of the embedded tissue was then cut using a rotary microtome, floated in a water bath onto a slide, and dried in an oven overnight. Mounted sections were stained using the Hematoxylin and Esosin regressive stain method. The stained tissue slides were examined under 10 x 4, 10 x 10 and 10 x 20 magnifications using a light transmission microscope. The sex and development stage of each gonad was determined microscopically and classified into one of four stages (undifferentiated, gametogenesis, mature and spent) according to the percentage of gonadal tissue versus connective tissue and the presence or absence of reproductive cellular organelles. The reproductive seasonality was determined by examining the proportion of adults in each development stage each month. Conch became reproductively active (gonads in gametogenesis, mature and spent phases) in April and remained active through December. All sampled adults were undifferentiated from January through March, indicating that there was no reproductive activity during these three months. Onset of sexual maturity or first sexual maturity was taken as the smallest size at which the mature/ripe stage was reached. Some conch were found to be reproductively active at a shell lip thickness of 3 mm; although the population Lso was not reached until a lip thickness of 19.5 mm. This study has provided the first conclusive estimates of the size at sexual maturity and spawning seasonality for queen conch in Barbados. Defining these parameters is important for informing management decisions and support management regulations regarding closed seasons and minimum legal sizes to protect spawning stock.