Reproductive strategy of spiny gurnard Lepidotrigla dieuzeidei Blanc and Hureau, 1973 from the south-eastern Adriatic Sea

This study provides the first data on the reproductive biology of the spiny gurnard Lepidotrigla dieuzeidei. A total of 1027 individuals were collected monthly from September 2011 to August 2012. The total length of the individuals in the sample ranged from 7.46 cm to 14.62 cm with a female to male ratio of 1 to 0.59. Positive allometric growth was observed for both females (b=3.07) and males (b=3.08). Variations of condition factor were similar in both sexes with mean values of 1.07 for females and 1.01 for males. The fish L. dieuzeidei had a long spawning period extending from November to July based on monthly values of gonadosomatic index. Histological analysis showed that this fish was multiple synchronous developments of ovaries with multiple spawning events. The ovaries were always represented with a group of primary oocytes and a diverse population of vitel-logenic oocytes, each specially recruited during the final stages of maturation in uniform or uneven phases. Batch fecundity was estimated gravimetrically using the hydrated oocyte method and was estimated to be around 558 to 10.230 oocytes per female. L. dieuzeidei is an important by-catch species and data from this study represent a valuable contribution to stock management.

Reproductive biology of the black-striped pipefish Syngnathus abaster Risso, 1827 (Pisces: Syngnathidae) in the Aegean Sea of Turkey

The paper presents the results of research on the reproductive biology of Syngnathus abaster – a species distributed in Çandarli Bay. For this purpose, seine nets were collected from a depth of 0.5–2 m in 15 minute periods between April 2013 and March 2014, and a total of 185 individuals were sampled. It has been determined that 94 individuals (50.81%) were females, 79 were males (42.70%) and 12 were immature (6.49%). The sex ratio was 1:0.84. The average length values in female, male and immature individuals were 111.5 ± 7.35, 109.9 ± 11.08 and 79.8 ± 5.30 mm, respectively. The maximum mean surface water temperature is in spring and summer seasons. When Gonadosomatic Index (GSI%) values were examined, the spawning period of the species was indicated as spring and summer. Three groups of species were identified as maturing (diameter: 0.61–1.20 mm), mature (diameter: 1.21–1.70 mm) and hydrated oocytes (diameter: 1.71–2.10 mm) in ovaries of female individuals. The number of eggs in the brood pouch of pregnant male fishes was on average 48 (mean ± SD = 48 ± 14.09 eggs, range: 23–78 eggs). The hydrated oocyte/total length relationship was: y = 0.8651x – 84.332 (n = 14, r2 = 0.64) and the number of eggs/total length relationship in the brood pouch of pregnant males was: y = 1.0168x – 67.715 (n = 33, r2=0.58).

Oocyte batch development and enumeration in the European anchovy (Engraulis encrasicolus)

An alternative method to the traditional hydrated oocyte (HO) method has been evaluated for the Sicilian anchovy, Engraulis encrasicolus. The method is based on the processing of ovarian whole mount images and the identification of the spawning batch in oocyte size frequency distributions and shows the advantage that it can be applied to various oocyte stages rather than strictly to the HO stage. Despite the peculiar elliptical shape of anchovy oocytes, this image analysis technique was fully successful since the yolked stage appeared to perform equally to the HO stage for anchovy batch fecundity measurements.

KEBERADAAN OVARIUM TRANSLUCENT SEBAGAI INDIKATOR MUSIM PEMIJAHAN IKAN LEMA Rastrelliger kanagurta (Cuvier, 1816) DI TELUK MAYALIBIT KEPULAUAN RAJA AMPAT

Tersedianya data dan informasi tentang musim pemijahan merupakan salah satu komponen biologi yang berperan penting bagi perlindungan sedian induk dalam rangka menjamin kelangsungan sumber daya ikan secara berkelanjutan. Ikan Lema merupakan ikan pelagis kecil yang termasuk dalam Genus Rastrelliger dengan sifat reproduksinya dikelompokkan sebagai partial spawner. Kelompok jenis ini sulit untuk ditentukan puncak musim pemijahannya karena tingkat kematangan sexual IV ditemukan setiap bulan. Oleh karena itu, suatu upaya penelitian telah dilakukan untuk mengetahui karakteristik ovarium tingkat IV dan hasilnya dapat dijadikan indikator yang ditujukan untuk menentukan puncak musim pemijahan jenis ikan Lema yang tergolong sebagai partial spawner. Ikan lema Rastrelliger kanagurta (Cuvier, 1816) merupakan hasil tangkapan utama nelayan di Teluk Mayalibit yang beroperasi dengan perahu tanpa motor yang dilengkapi dengan lampu pada periode gelapbulan. Pengukuran dilakukan pada kurun waktu bulan Maret 2011 sampai dengan Februari 2012. Pengamatan terhadap sejumlah 656 specimen ovarium tingkat IV dengan rerata 55 spesimen/bulan) yang telah dikumpulkan pada periode tersebut. Analisis makroskopik difokuskan terhadap gonad betina (ovarium) pada tingkat IV yang diklasifikasikan sebagai ovarium translucent. Hasil analisis menunjukkan bahwa nilai frekuensi sampel bulanan terhadap ovarium translucent (51 – 100 % hydrated oocyte) memperlihatkan bahwa puncak musim pemijahan terjadi pada September (15,4 % dan 24,0 %), Oktober (12,8 dan 9,4 %), dan November (17,9 % dan 13,2 %). Temuan ini memberikan indikasi nyata bahwa tingginya frekuensi kejadian ovarium translucent dapat dijadikan indikator penentuan puncak musim pemijahan.

Spawning and fecundity of king weakfish, Macrodon ancylodon, in the Río de la Plata estuary, Argentina–Uruguay

The reproductive biology of the king weakfish, Macrodon ancylodon, inhabiting the estuarine waters of the Río de la Plata (Argentina–Uruguay), was studied using macroscopic and histological analysis of the gonads. The samples were collected from commercial landings and from three research cruises carried out between 1999 and 2001. King weakfish is a multiple spawner with indeterminate annual fecundity. Spawning of this species extends from October to March with two main peaks of gonadal index in November and March. Based on the incidence of females with new postovulatory follicles, the evening near sunset was the estimated time of spawning for M. ancylodon. Spawning frequency, determined using the percentages of females with postovulatory follicles, was about 17% during March 2001, indicating that females spawn once every six days at the second peak of the reproductive season. Batch fecundity ranges from 12,400 to 225,700 hydrated oocytes and was fitted to a linear function of total length and ovary-free female weight. The number of hydrated oocytes decreased at the end of the spawning season. In addition, a decline in hydrated oocyte size and weight was also observed during this period.