SEBARAN UKURAN DAN PERTUMBUHAN HIU MARTIL (BY CATCH) YANG DIDARATKAN DI PANGKALAN PENDARATAN IKAN (PPI) UJONG BAROH MEULABOH

Hammerhead shark is a type of predator shark belongs to the family of Sphyrnidae. This shark is so aggressive in hunting prey such as fish, squid, and shrimp. The hammerhead shark in Indonesia is included in Appendix II of CITES and has been a special concern in the field of capture fisheries. The aim of the study was to see the size spread, the number of catches, the first size caught, the age growth and the genital ratio of the hammerhead sharks caught with the base fish net. The study was conducted from October to December 2019. The shark measurement was performed once in 2 weeks. Sharks caught by the gills of the base (buttom gilt net) were measured using a roll meter. The collection of hammerhead sharks included total length (TL), number of catches and genital ratio. The analysis was done descriptively using the ELEFAN I existing on Sofwere FiSAT II. The results showed that the hammerhead sharks caught with an gill net of 65 tails from October to December 2019 were taken on the male genital. The total size spread of female malletic sharks were between 61.5-131.5 cm and male hammering sharks between 61.5-111.5 cm. The morphologically spread of the female hammerhead was relatively longer than the male shark. The male hammerhead shark was first captured at a length of 117.9 cm and a female hammerhead shark at a size of 106.2 cm. Hammerhead shark growth by following the curve of von Bertalanffy mallet were male Lt = 138,08 (1-exp (-0.480 (t + 0.0487)) and female mallet shark Lt = 138,08 (1-exp (-0.430 (t + 0.0434)). Such equations can be known by using the relationship curve model between the age and length of fish.

Biological aspects of juvenile great hammerhead sharks Sphyrna mokarran from the Arabian Gulf

The life history of the critically endangered great hammerhead Sphyrna mokarran was examined using samples collected from commercial fisheries operating in Saudi Arabian waters of the Arabian Gulf. In all, 105 specimens (47 males, 58 females), with a total length (TL) ranging from 67.0 to 236.0cm, were examined between April 2016 and November 2019. All individuals were immature. A neonate measuring 67.0cm TL caught in early June suggested the parturition period of this species was during May and June. Vertebrae under the first dorsal fin from 69 individuals (30 males, 39 females) were processed. Three age groups, from 0+ to 2+ years old, were identified by vertebrae analysis. Based on the relationship between vertebral central diameter and TL, the Fraser–Lee approach was used to back-calculate the growth history of TL. A two-parameter von Bertalanffy growth function provided the best fit to describe early growth of great hammerheads during 0–2.9 years of age based on observed and back-calculated length-at-age data. The asymptotic lengths and k values were estimated to be 256.8cm TL and 0.449 year–1 respectively. This study provides the first life history information of great hammerhead sharks in the north-western Indian Ocean.

Assessing the Efficacy of A Marine Reserve to Protect Sharks With Differential Habitat Use

Spatial management through the implementation of marine protected areas is one strategy to limit the extraction of sensitive marine species. Understanding the area used by marine life is thus a key step towards the evaluation of the management framework and efficacy of a protected area. To provide information of the protective coverage of the Galapagos Marine Reserve (GMR), we assessed the habitat utilization distribution (UD) of hammerhead and blacktip sharks in the GMR. Fifteen hammerhead sharks and 27 blacktip sharks were tagged with SPOT and SPLASH satellite tags in the north and south-central regions of the GMR between 2007 and 2012. Our results show nearly 90% of hammerhead shark’s UD was enclosed by the reserve boundary during the cold season (June-October), yet this decreased to only ~30% with the advent of the warm season (December-April). Conversely, blacktip sharks’ UD was 100% enclosed by the reserve boundaries in all seasons. Season and depth were the most important environmental parameters defining the UD of hammerhead sharks; whilst year and eddy kinetic energy were the most important parameters for blacktip sharks. These findings suggest the size of the GMR may be effective for blacktip sharks but seasonally effective for hammerhead sharks.