Size-frequency, length-weight, and length-length relationship of two species of halfbeaks (Family: Hemiramphidae) from the north coast of the Yucatan peninsula, Mexico

Size-frequency, length-weight, and length-length relationships for Hemiramphus brasiliensis (Linnaeus, 1978) and Hyporhamphus unifasciatus (Ranzani, 1841) from the north coast of the Yucatan peninsula in the Gulf of Mexico were studied. All specimens were collected from the artisanal fishery of halfbeaks, which is under an exploratory fishery license. Five thousand two hundred-one individuals (5,134 H. brasiliensis and 67 H. unifasciatus) were sampled and analyzed. The size-frequency analysis showed that individuals of H. brasiliensis among 31.5 to 34.5 cm of total length (TL) class dominated the fishery samples; however, the separation index (≥2) detected two modes in the last months of the year, identifying a cohort with a length below the average (24.5 to 26.5 cm TL). The isometric growth pattern was found in females and pooled sex in H. unifasciatus, and positive allometric growth was found in males and H. brasiliensis. The TL was 9 and 4.5% greater than the fork length for H. brasiliensis and H. unifasciatus, respectively. The size of H. brasiliensis (45.5 cm TL) exceeds the reported in previous studies from the Gulf of Mexico and the Mexican Caribbean Sea, and a new record of maximum length for H. unifasciatus (31cm TL) was reported to the FishBase database.