Seven-gill shark in southern Patagonia

What is it about?

Between 2004 and 2007, contests editions and the recreational fishery for the Broadnose sevengill shark, Notorynchus cepedianus, were monitored in Natural Reserves of Ría Deseado (RD, a breeding area for the Patagonian smoothound) and Peninsula de San Julian (SJ), Southern Patagonia, Argentina. Sharks catch composition by sex; total length (TL) and weight (W) were recorded. Reproductive status was assessed from the literature. Juvenile females dominated the catches in both areas during the 4-year period. In RD the females of the seven gill sharks were larger than in SJ (t=5.389, d.f.=73, p<0.01). Mean TL in RD was 1,781 mm (sd=245.08; range 1,150–2,320 mm TL) and in SJ the mean TL was 1,484 mm (sd=196.10; range 1,210–2,000 mm TL). No differences between localities were detected in the case of males for the TL (t=1.520, d.f. =34, p>0.05). Mean TL in RD was 1,616 mm (sd=245.83; range 1,100–2,050 mm TL). In SJ the mean TL was 1,508 mm (sd=184.26; range 1,250–2,000 mm TL). The TL-W relationships are W (g) = 2.77E-06 TL (mm) 3.0634 for females and W (g) = 1.05E-05 LT (mm) 2.8858 for males. No significant differences were found between the slopes of the logTL–logW relationship of males and females (t=1.058, d.f.=107, p>0.05). In RD sex ratio (female:male) was 3.2:1, which results significantly different from 1:1 (χ2=8.64; p>0.05). However in SJ sex ratio was 1.3:1 but this differences were not statistically significant to 1:1 (χ2=0.5; p>0.05).The conclusions of this survey is that RD and SJ may act as secondary breeding areas of N. cepedianus, and they are reported as the most southern of Southwestern Atlantic for this species.

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