Life cycles and feeding habits of Syngnathus taenionofus and S. abasrer (Pisces, Syngnathidae) in a brackish bay of the Po River Delta (Adriatic Sea)

We investigated the population structure, life cycles and gut contents of 2 species of pipefish, Syngnathus taenionotus and S. abaster, in a brackish embayment of the PO River Delta (North Adriatic Sea).These 2 species inhabit the nearshore environment of the bay where the sandy bottom is covered by macroalgae, and were sampled for 1 yr.The main differences in life history traits between S. taenionotus and S. abasterrespecitvely can be summarized as follows: life span is about 24 vs 17 mo; reproductive season begins in February vs March, and lasts 5 vs 4 mo; average length of fingerlings at the time they hatch from the male brood pouch is 20.3 (k1.2) vs 13.5 (fl.O) mm; egg incubation period is 2 mo vs 1 mo; average number of ripe eggs per mature ovary is 46 (+ 9) vs 104 (+ 40); average number of embryos incubated by male is 84 (f 17) vs 109 (f 27).Finally, the sex ratio in the reproductive population is more male-biased in S. taenionotus than in S. abaster.The 2 species probably do not compete for food resources, remaining almost completely segregated in 2 different foraging micro-habitats during most of their life span.The new-born spring individuals of both species feed almost exclusively on harpacticoids of the genus Tisbe.As they mature, S. abaster continue to prey on phytal organisms while the larger S. taenionotus become zooplanktivorous.