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Latin american journal of aquatic research

versión On-line ISSN 0718-560X

Lat. Am. J. Aquat. Res. vol.47 no.3 Valparaíso jul. 2019 

Short Communication

First description of a deceased juvenile whale shark Rhincodon typus in La Paz Bay, Mexico with comments on morphometry and age estimates

Darren Whitehead1 

Felipe Galván-Magaña1 

Katherin Soto-López1 

Diego Juaristi-Videgaray1 

Fabián Cervantes-Gutiérrez1 

Edgar Eduardo Becerril-García1  2 

1Instituto Politécnico Nacional, Centro Interdisciplinario de Ciencias Marinas, La Paz, BCS, México

2Pelagios Kakunjá A.C., La Paz, BCS, México


This paper is the first report with morphometric measurements in the Eastern Tropical Pacific of a deceased 5.48 m juvenile whale shark Rhincodon typus, from a rare stranding in La Paz Bay in the Gulf of California, Mexico. Biological measurements and age estimation are provided by the analysis of photographs and growth in rings from vertebrae.

Keywords: Rhincodon typus; stranding; vertebrae; age; Gulf of California

The whale shark Rhincodon typus (Smith, 1828) represents the monotypic family Rhincodontidae (Compagno et al., 2005). It has a circumglobal distribution, with occurrences reported in all tropical and warm temperate waters, except for the Mediterranean Sea (Compagno et al., 2005). The species habitat can range from an open ocean environment to shallow coastal basins, with a depth distribution from near-surface waters to more than 1,928 m (Tyminski et al., 2015). It has a yolk sac viviparity mode of reproduction and has been reported to carry as many as 300 pups (Joung et al., 1996). Depending on the location, size at maturity for male sharks ranges between 7-9 m in total length (TL), while in the female's maturity is estimated to be of 9 m TL, based on visual and photogrammetry estimates (Acuña-Marrero et al., 2014; Rohner et al., 2015).

In the Gulf of California, whale shark aggregations are known to occur in areas such as Los Ángeles Bay or La Paz Bay, where high zooplankton abundance has been reported (Ketchum et al., 2013). As this species has been observed feeding on prey items such as the euphausiid Nyctiphanes simplex, the copepod Acartia spp., other crustacean's larvae and fish eggs (Ketchum et al., 2013).

The whale shark is an internationally protected species highly susceptible to the fisheries that occurs near coastal aggregation sites (Pierce & Norman, 2016). Due to the global decline in whale shark populations, the species status was raised to endangered by the International Union for Conservation of Nature and Natural Resources in 2017 (IUCN, 2017). Also, the species is listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), and it is protected by Mexican regulations in the NOM-059-SEMARNAT-2010 and NOM-029-PESC-2006 by a national fishery ban for this species. Although the presence of whale sharks in the Gulf of California and the Mexican Caribbean is predictable, there are no published records of stranded whale sharks, age estimations or anatomical observations that can be useful for ecological, phylogenetic or further basic biological studies (Whitehead et al., 2018). The objective of this study was to provide traditional morphometric measurements from a deceased juvenile whale shark in the Gulf of California, through anatomical information, as well as age estimation from the analysis of its vertebrae.

The shark was found deceased in shallow waters off the Ensenada de La Paz, Mexico (24°9’45”N, 110°24’3”W) on the 16th February 2018 (Fig. 1).

Figure 1 Location of the stranded juvenile whale shark in La Paz Bay, Mexico. 

When found, the shark presented seven marks on its head and the anterior part of the pectoral fins, potentially caused by lead fishing sinkers from a net. The probable cause of death was asphyxia provoked by fatigue. However, a more detailed investigation of the species from the necropsy work is currently ongoing, and the cause of death is still not confirmed. The carcass was transported to the Centro Interdisciplinario de Ciencias Marinas (CICIMAR-IPN) by local scientists and local environmental authorities to perform a necropsy. On land, pictures were taken, and morphometry was developed before the anatomical analysis of the body (Table 1).

Table 1 Morphometry in cm and proportion of the whale shark Rhincodon typus specimen stranded in La Paz Bay, Mexico. 

Measurements Length
Total length (TL) 548.0 100.0
Precaudal fin length (PCL) 439.0 80.1
Fork length (FL) 485.0 88.5
Pre-first dorsal fin length (PD1) 200.0 36.5
Pre-second dorsal fin length (PD2) 366.0 66.8
Head length (HDL) 81.0 14.8
Mouth width (MOW) 103.0 18.8
Spiracle length (SPL) 3.0 0.5
Interorbital space (INO) 80.0 14.6
Eye length (EYL) 3.9 0.7
Eye height (EYH) 4.2 0.8
Intergill length (ING) 44.0 8.0
First dorsal-fin length (D1L) 67.5 12.3
First dorsal-fin height (D1H) 39.3 7.2
Second dorsal-fin length (D2L) 35.0 6.4
Second dorsal-fin height (D2H) 17.0 3.1
Pectoral fin base (P1B) 67.0 12.2
Pectoral-fin anterior margin (P1A) 95.0 17.3
Pelvic-fin length (P2L) 32.0 5.8
Pelvic-fin height (P2H) 16.0 2.9
Anal-fin length (ANL) 36.0 6.6
Anal-fin height (ANH) 20.0 3.6
Dorsal caudal-fin margin (CDM) 143.0 26.1
Caudal-fin fork length (CFL) 39.0 7.1
Preventral caudal-fin margin (CPV) 77.0 14.1
Clasper inner length (CLI) 33.0 6.0
Clasper outer length (CLO) 23.0 4.2
Trunk width (TRW) 245.0 ---
Tail width (TAW) 170.0 ---
Caudal-fin peduncle width (CPW) 62.5 ---

The specimen was identified as Rhincodon typus by its checkerboard pattern of light spots and stripes over a dark body, flattened head with a nearly terminal mouth, and the presence of three prominent ridges along its dorsal flanks (Compagno et al., 2005). Total length (TL) of the shark was 5.48 m, and it was classified as a juvenile male by the presence of slightly calcified claspers with the inability to fully rotate them (Compagno et al., 2005; Acuña-Marrero et al., 2014; Rohner et al., 2015). A bilobed liver was extracted and measured 1.54 and 1.52 m in TL length for the right and left lobe, respectively. The stomach was emptied and measured 1.15 m in length and 0.75 m in width. The spiral valve measured 1.35 m in length and 0.25 m in width, with no evidence of the presence of endoparasites in the first section of the intestine. The white muscle was limp and highly greasy, while the red muscle fibers were small and consistent in their density. Dermal hard tissue was discovered in the posterior part of the esophagus (Fig. 2), which may be related to an auxiliary feeding structure to prevent the loss of stomach content.

Figure 2 a) Reported whale shark from the stranding in La Paz Bay, Mexico, b) detail of the anterior part of the esophagus, c) sagittal cut of the vertebrae. 

Vertebrae were extracted from the region under the first dorsal fin, as these vertebrae are acknowledged to be relatively homogeneous and retain the largest radius and clearer growth bands (Campana, 2001). These samples were immediately frozen in the laboratory of CICIMAR-IPN. Before analysis, the vertebrae went through an extensive cleaning with a scalpel and embedded using ethanol (70%). The vertebrae lateral diameter measured 63.14 mm, dorsal diameter 62.65 mm and height 50.8 mm. The vertebrae were cut both sagittal and transversally, with the use of a transmitted light aided for the counting of the growth bands. A visual count of the growth rings totaled 17 bands with translucent edges (Fig. 3).

Figure 3 Longitudinal cut of the whale shark vertebrae reported in this study, with the focus (F); birthmark (▲); Corpus calcareum (C); Intermedialia (I); and 17 growth rings (•). 

Age was estimated by using the total length of the deceased shark (Table 1) and the growth function with the inverse of the model t=ln([1(LT/L)]/b)/k from the two-parameter Von Bertalanffy (1938) growth function, and b=[(LL0)/L] and t=t0ln(1[LT/L])/k for the three-parameter von Bertalanffy models. Where k is the growth constant, to is the age at length zero, Lt is the total length recorded in this study, L is the asymptotic total length and Lo is the size at birth which is expected to be 0.64 m adopted from the largest full-term embryo data of Joung et al. (1996). Using previous von Bertalanffy growth models for whale sharks by Wintner (2000) and Hsu et al. (2014), it was possible to estimate that the shark was 18-19 years old, adopting the criteria of the formation of a single annual band per year. However, the age of the shark was assessed to be 17 years old by the visual observations of the vertebrae growth rings (Table 2).

Table 2 Estimation of the reported whale shark using the model parameters of two and three-parameters with von Bertalanffy (1938). k: growth constant, L: asymptotic total length, t0: age at length zero. 

Parameter Wintner (2000) (annual band) Hsu et al. (2014) (annual band) Hsu et al. (2014) (biannual band)
k 0.032 0.021 0.037
L(m) 11.79 15.34 16.8
t0 -0.85 --- ---
Estimated age (years) 18.68 19.01 9.62

Records of whale shark strandings have been reported in other countries such as South Africa, India, Australia and Mozambique (Kakini et al., 1959; Beckley et al., 1997; Speed et al., 2009; Rohner et al., 2013). These studies have been useful in terms of fatty acids, stomach contents, and biogeography, however, detailed morphometric data is usually not provided. The presented results in this study are consistent with the information reported by Hsu et al. (2014) from juvenile whale sharks of the north-western Pacific. However, the use of further detailed morphometry and age estimations of mature whale sharks could complement the information regarding morphometry, basic biology and demography of each population. Additionally, the obtention of morphometric data from stranded animals with the application of photogrammetry techniques during the monitoring of living sharks is suggested, as this could generate accurate information for the assessment of growth and maturity length, phylogenetics and potential anatomical changes during the life cycle of R. typus (Rohner et al., 2011, 2015; Jeffreys et al., 2012; Whitehead et al., 2018).


We thank the Procuraduría Federal de Protección al Ambiente, Museo de la Ballena y Ciencias del Mar, MMARES A.C./Red de Varamientos de La Paz, Roberto Robles, C. Ballinez-Ambriz and C. López-García for all their support. We also thank two anonymous reviewers for the improvement of our manuscript, D. Bernot-Simon for the English review, the Instituto Politécnico Nacional for funding through grants from the COFAA (Comisión de Operación y Fomento de Actividades Académicas), the EDI (Estímulo al Desempeño de los Investigadores) and CONACyT for the provided scholarships. This study was conducted under the permit SGPA/DGVS 05605/17 provided by the Dirección General de Vida Silvestre from the Subsecretaría de Gestión para la Protección Ambiental of SEMARNAT.


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Received: April 12, 2018; Accepted: March 26, 2019

Corresponding author: Felipe Galván (

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