Oral Presentation Australian Society of Fish Biology and Oceania Chondrichthyan Society Conference 2016

First excursions into the ‘black box’ period of the blackspot seabream Pagellus bogaraveo: a missing piece of a deep-sea life cycle puzzle (#14)

João Teixeira 1 2 , Jorge Fontes 3
  1. Dept. of Oceanography and Fisheries, University of the Azores, Horta, Portugal
  2. School of BioSciences, University of Melbourne, Melbourne, Australia
  3. IMAR - Institute of Marine Research , Dept. of Oceanography and Fisheries, University of the Azores, Horta, Portugal

The blackspot seabream, Pagellus bogaraveo, is ecologically and commercially one of the most important demersal species in the archipelago of the Azores. Its exploitation around the islands has increased due to the collapse of the fishery in continental waters. Despite the importance of recruitment processes in marine fisheries productivity, research has been focused primarily on the general aspects of the species’ biology and population dynamics, and as consequence little is known about the early life stages in the wild. My work focused on the understanding and characterization of its early life history, recruitment and post-settlement dynamics. To achieve these goals I used two methods: 1) underwater visual census, i.e., recruit counts, to investigate the temporal dynamics of recruitment, and 2) the analysis of juvenile otolith microstructure to investigate the early life history traits. Recruitment surveys were conducted monthly from April 2011 to May 2012 in Faial island, Azores. The results showed clear seasonal patterns of recruitment. Recruitment peaks were observed in April and May in two consecutive years, followed by a clear succession in the juvenile size structure over the following months culminating with the disappearance of bigger sized recruits from inshore waters during winter months. Otolith daily increment formation was validated which allowed us to retrospectively study the early life history of blackspot seabream. After interpreting the otolith microstructure and identifying the settlement mark, we were able to determine age, length-at-age relationship, pelagic larval duration (37.37±0.28 d), estimated size at settlement (13.50±0.17 mm), and average growth rates. Growth rates were significantly higher after settlement (16.82±0.47 mm d-1) compared to the larval stage (7.11±0.08 mm d-1). After back-calculating birth dates and grouping individuals by batch, comparison tests were used to investigate if there were significant differences in early life history traits among batches.