The life history of the invasive mullet, Osteomugil engeli (Bleeker, 1858) in Hawaiian estuaries

Abstract

Although mullets (Mugilids) are important estuarine fishes across the world, the biology of many species of mullet have yet to be determined. This is of concern for mullets that are introduced species with unknown impacts on native ecosystems. Here we assess the life history of Osteomugil engeli, an introduced species in Hawai'i. Two populations (Hilo Bay estuary, Hawai'i Island and Maunalua Bay estuary, Oahu) were compared to determine population demographics, spawning season, and size and age at maturity. There were no differences observed between life history metrics between populations sampled. O. engeli had year round spawning with recruits and adults co-occurring in similar habitats throughout the year. There was no difference in size (L 50 ) and age (A 50 ) at sexual maturity for females and males (L 50 : χ 2 = 0.39, p value =0.53; A 50 : χ 2 = 0.29, p value = 0.59), with O. engeli reaching sexual maturity at 140.1 mm (CI: 139.5-141.6 mm) and 208 days (CI: 204.2-220.9 days). We observed a 4:1 female to male sex ratio and females were found to be on average 23 mm larger than males (t = 7.19, p value<0.01). O. engeli life history is compared to native species in Hawai'i and among other Mugilids that have been introduced elsewhere. Life history comparisons suggest that introduced mullet populations are better able to respond and adapt to changing habitat and environmental conditions than the native mullet.