Bio-Ecology of the Oldest Lessepsian Fish Atherinomorus forskalii (Pisces: Atherinidae)

Although Atherinomorus forskalii is the oldest lessepsian fish species with a widespread distribution range, there have not been any study about its biological and ecological features. Therefore, we aim to understand its effects on coastal ecosystems by determining its feeding ecology and life span. Four hundred sixty-two specimens were obtained with Sabiki rigs from the Turkish coast of the Levantine Sea. The minimum, maximum and mean length values of the samples were determined as 4.5 cm, 12 cm and 8.2 cm ±0.07 respectively. In winter and spring, the species main food item was represented by pelagic gastropods, while copepods in summer and insects in autumn were the main food items. Although A. forskalii prefers small-sized invertebrates, it is observed that they consume juvenile fish larger than one third of their size. Its wide diet preference shows that it is an opportunistic feeder. These findings represent that A. forskalii feeds on native species and also is in food competition since its dietary overlaps. Ages were calculated between I and III, and the second age group was dominant with a ratio of 52.8%. The highest spawning activity took place between April and early July. The hepatosomatic index (HSI) and gonadosomatic index (GSI) values were calculated monthly, and they reached the highest points in May and June, respectively. The results showed that this small fish, which has been deprived of scientific interest until now, has been determined to have a bio-ecological superiority according to its syntopic species. Thus, it is revealed that it has a more negative impact on the coastal ecosystem than expected.