Validated age and growth of the leopard shark, Triakis semifasciata, with comments on reproduction

Abstract

SynopsisThe age, growth, and sexual maturation of the leopard shark, Triakis semifasciata, from central California were studied. Growth band counts in vertebral centra of 162 leopard sharks produced von Bertalanffy growth curves with L,, K. and t, parameters of 1536mm. 0.082, and -2.31, respectively, for both sexes combined. The L, value for females (1602mm TL) was slightly but insignificantly higher than for males (1499 mm TL), but the K and t, values were almost identical. Seasonal changes in size modes of young-of-theyear leopard sharks, centrum edge characteristics, and growth and tetracycline mark-recapture from the field were used to validate annual deposition of vertebral centrum band pairs. Sexual maturity was evaluated by the gonads and presence of sperm and eggs; males mature at 7 yr and at about 63% of asymptotic length, and females mature at 10 yr, and at about 72% of asymptotic length. This slow growth, late maturity, and relatively low fecundity may increase their susceptibility to over-exploitation.

Growth of Lesser Spotted Dogfish (Scyliorhinus caniculaL., 1758) in the Cantabrian Sea, Based on Tag-recapture Data

“…There is evidence that tagging may reduce or halt growth in some sharks such as lemon shark studied by Manire and Gruber, (1991), and it has also been suggested in other sharks by Stevens, (1990), Cailliet et al, (1992, Kusher et al, (1992) and Natanson et al, (1999). There is no evidence that this occurs in the lesser spotted dogfish.…”

“…Cailliet et al, (1992) obtained better results with the Gulland and Holt (1959) method than Fabens (1965) for the Pacific angel shark (Squatina california) although in this case K was underestimated. The Fabens (1965) method can lead to biased estimates because its basic premise, that tagged individuals are at large for equal time periods, is often violated with sharks (Chien and Condrey, 1987).…”

“…Estimates based on this model are very close to those of Gulland and Holt (1959) with the exception of females which show a meaningless high growth rate. However, this method is not well established, because it uses a coefficient of variation to derive the best estimates of K (Cailliet et al, 1992). Models that incorporate individual variability in ∞ L produced the best fit in both sexes, while Sainsbury (1980) model presents the best fits for males and females independently.…”

Habitat use, residency, and seasonal distribution of female leopard sharks Triakis semifasciata in Elkhorn Slough, California

“…2). Based on age and growth estimates from Kusher et al (1992), one shark was a juvenile (<105 cm TL) and the rest were adults (>105 cm TL). Sharks ranged in length from 91 to 132 cm TL (mean 119.4 cm ± 4.8 SE).…”

“…3). As it was highly unlikely that the sharks left the slough without being detected by any of the Kusher et al (1992) (A: adult,105 cm TL; J: juvenile, 105 cm TL), date and location of tagging (E: ESNERR; MC: main channel), total length (TL), dates monitored (time from initial tagging to last detection, days indicates the number of days during this time frame that the shark was known with certainty to be in Elkhorn Slough; * indicates that sharks were likely in the slough until the receivers were removed on 3 Feb 2005), and total number of detections at VR1 receivers receivers, this suggests that the sharks remained in ESNERR or the upper region from the time of their last detection at Receiver 5 or 6 until some period after the receivers were removed. Although we believe that these sharks remained in either ES-NERR or the upper region, the analysis of the use of the different regions of the slough by these sharks only included the period of time until their last detection in order to be conservative.…”