Colonization, hatching dates, and growth rates of juvenile Hyporhamphus picarti (Hemiramphidae), in the Nador lagoon (NE Morocco)
The Nador lagoon, located in the northeastern part of the Moroccan Mediterranean coast, was sampled with a beach seine at six stations during different seasons, from 2012 to 2014. The African halfbeak Hyporhamphus picarti was collected among the fish species and some aspect of its biology and ecology (coloni- zation of the lagoon, spawning period and growth) was described for the first time. This species was found only in late summer and autumn, and all the individuals captured were juveniles, indicating that the lagoon serves as an important nursery for this species. Growth increments in the lapilli otoliths were used to investigate its early life history. Assuming that the primary increments are deposited daily, age and hatching dates were determined by counting these increments in juvenile fish collected during late summer and autumn. The estimated ages of juveniles ranged from 39 to 58 days (TL: 68.10 ± 15.19 mm) in 2012, and from 42 to 77 days (TL: 101.03 ± 28.77 mm) in 2013. Juveniles collected in 2013 had significantly higher growth rates (2.35 mm. d−1) than those collected in 2012 (1.88 mm. d−1) regardless of temperature. For both years, the average otolith increments width increased until about the 25th day (corresponding to a size of about 28 mm TL), and then decreased. Back- calculated hatching dates of juveniles collected in the lagoon indicated that they hatched in summer, from June to September. These results indicate that H. picarti has a short spawning period during the warm period and uses the lagoon as a nursery ground in late summer and autumn.