Geographic variation in life‐history traits of the endemic kite skate Dipturus chilensis (Batoidea: Rajidae), along its distribution in the fjords and channels of southern Chile

Abstract

Life‐history traits of kite skates Dipturus chilensis were examined from two regions (c. 2286 km apart) in the sheltered fjords and channels of southern Chile. A total of 482 and 403 specimens were collected from the southern fjords (c. 42–46° S) and the fjords of Chilean Patagonia (c. 51–54° S), from September 2003 to 2004, respectively. Vertebra marginal increment analysis indicated an annual deposition of growth rings which was completed during the winter months. For each region, von Bertalanffy growth parameters showed that females attained a larger asymptotic size, L∞, had a lower growth coefficient, K, and lived longer than males. Growth analysis indicated that D. chilensis from the Patagonian fjords had a longer life span (females: 22 v. 21 years; males 19 v. 17 years), attained a larger L∞ (females: 150 v. 136 cm; males: 122 v. 118 cm total length, LT) and had a lower K value (females: 0·087 v. 0·104; males: 0·110 v. 0·116) than their counterparts in the southern fjords. Comparisons with previous studies indicated that D. chilensis from both southern and Patagonian sheltered fjords had larger L∞, and grew more slowly than their counterparts from central‐southern Chile (L∞= 119–123 cm, K= 0·123–0·127), suggesting latitudinal variations in growth. Females attained sexual maturity later than males in both regions. For both sexes, lengths at 50% maturity (L50%) between regions were similar (females: c. 103 cm; males: c. 87 cm LT); however, D. chilensis from Patagonia appeared to mature 1 year earlier (females: 13 v. 14 years; males: 10 v. 11 years). Specimens from Patagonia had a lower ovarian fecundity than those from the southern fjords. An increase in the proportion of mature females and males during summer, suggests that the reproductive peak occurs in this season, and no regional differences were found. The size of the egg cases increased with maternal LT and these were longer in Patagonia. The information provided here represents the first evidence of regional variations in life‐history traits for elasmobranchs in the south‐eastern Pacific.

Reproductive biology of the eyespot skate Atlantoraja cyclophora (Elasmobranchii: Arhynchobatidae) an endemic species of the Southwestern Atlantic Ocean (34ºS - 42ºS)

“…There are many hypotheses to explain this fact, these variations could be a consequence of oceanographic conditions, the effect of fishing pressure (Mabragaña, Cousseau, 2004), or the result of phenotypic plasticity (Licandeo, Cerna, 2007). The maximum TL and size at maturity recorded here were similar to that previously reported in northern Patagonian waters and greater than the registered for individuals from southern and southeastern Brazil (Oddone, Vooren, 2005;Oddone et al, 2008).…”

“…However, the size of the egg cases of A. cyclophora examined in this work were similar those recorded by from southern Brazil. According to Licandeo, Cerna (2007), the females of Zearaja chilensis (Guichenot, 1848) of the southernmost distribution from southern Chile would invest more energy in the production of larger egg cases instead of more quantity of eggs, than females of the northern region. More complementary studies of the ovarian fecundity of A. cyclophora are necessary to better understand their reproductive traits.…”

Reproduction of the pelagic thresher shark Alopias pelagicus in the equatorial Pacific

“…This reveals differences in reproductive parameters in the species that might be influenced by both life history and environmental traits. Such regional (Yamaguchi et al, 2000;Lombardi-Carlson et al, 2003;Licandeo & Cerna, 2007).…”

Age, growth, and age at sexual maturity of the commercially landed skate species,Dipturus chinensis(Basilewsky, 1855), in the northern East China Sea

“…Together considering a strong correlation between TL and the radius identified for each sex, it is therefore concluded that all fish reach a similar body size at the first growth band formation (i.e., summer to autumn) regardless of their hatching dates. Although there are several reports on age and growth of skate species with year-round oviposition (Frisk & Miller, 2006;Kadri, Marouani, Bradai, & Bouaïn, 2013;Kadri et al, 2012;Licandeo & Cerna, 2007;Richards, Merriman, & Calhoun, 1963), to our knowledge, this is the first study based on solid evidence reporting such a unique trait in skate. Further studies are Previous studies have suggested that band formation might be related to physiological changes that correspond to the seasonal variation of environmental parameters, such as temperature and photoperiod, as well as the reproductive state (Goldman, 2004;Simpfendorfer, 1993).…”