Beak Growth Pattern of Purpleback Flying Squid Sthenoteuthis Oualaniensis in the Eastern Tropical Pacific Equatorial Waters
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See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/273483351 Beak growth pattern of purpleback flying squid Sthenoteuthis oualaniensis in the eastern tropical Pacific equatorial waters Article in Fisheries Science · March 2015 DOI: 10.1007/s12562-015-0857-8 CITATIONS READS 2 100 6 authors, including: Zhou Fang Xinjun Chen Shanghai Ocean University Shanghai Ocean University 22 PUBLICATIONS 36 CITATIONS 170 PUBLICATIONS 700 CITATIONS SEE PROFILE SEE PROFILE Bilin Liu Yong Chen Shanghai Ocean University University of Maine 38 PUBLICATIONS 268 CITATIONS 214 PUBLICATIONS 2,226 CITATIONS SEE PROFILE SEE PROFILE All in-text references underlined in blue are linked to publications on ResearchGate, Available from: Zhou Fang letting you access and read them immediately. Retrieved on: 28 August 2016 Fish Sci DOI 10.1007/s12562-015-0857-8 ORIGINAL ARTICLE Biology Beak growth pattern of purpleback flying squid Sthenoteuthis oualaniensis in the eastern tropical Pacific equatorial waters Zhou Fang · Luoliang Xu · Xinjun Chen · Bilin Liu · Jianhua Li · Yong Chen Received: 29 August 2014 / Accepted: 13 December 2014 © Japanese Society of Fisheries Science 2015 Abstract Cephalopod beaks maintain a stable morphol- length, and lower lateral wall length, which showed lin- ogy, implying that they can be used to explore ecological ear relationships with ML. The relationships between BW influences on squid life history. Understanding the beak and the six beak variables were best fitted with power growth pattern can help us to improve knowledge of the functions, and these functions can be used to estimate trophic characteristics of squids and to estimate squid squid biomass from beak variable values. All of the beak biomass. Sthenoteuthis oualaniensis is widely distrib- morphological variables varied according to the maturity uted in eastern tropical Pacific equatorial waters and has stage of the squid. Results of a post hoc comparison sug- been caught commercially by Chinese squid jigging fleets gested that the values of beak morphological variables for since 2011. In this study, we randomly took 220 samples immature squids (maturity stages I and II) showed signifi- of S. oualaniensis with mantle lengths (ML) of between cant differences from the corresponding values for mature 119 and 351 mm and body weights (BW) of between 45 squids (maturity stages III–V). These differences may and 1975 g and measured six beak morphological vari- result from changes in diet that occur during maturation, ables for each sampled squid. The relationships between which affect the relevant mandibular muscle strength. The ML and all of the beak variables were power functions, most common pigmentation stages (PS) encountered were except for upper lateral wall length (ULWL), upper crest II–V. The relationships of PS to ULWL and lower wing length were best described by exponential functions. Beak morphology and pigmentation of S. oualaniensis tended Z. Fang · L. Xu · X. Chen · B. Liu · J. Li College of Marine Sciences, Shanghai Ocean University, to change markedly with ontogenetic stage. It is easy to Hucheng Ring Road 999, Lingang New City, 201306 Shanghai, separate mature and immature squids based on their PS. China This study provides important biological information on S. oualaniensis. Z. Fang · L. Xu · X. Chen (*) · B. Liu · J. Li · Y. Chen Collaborative Innovation Center for Distant-Water Fisheries, 201306 Shanghai, China Keywords Sthenoteuthis oualaniensis · Beak · e-mail: [email protected] Morphology · Growth pattern · Pigmentation · Eastern Tropical Pacific X. Chen · B. Liu · J. Li The Key Laboratory of Shanghai Education Commission for Oceanic Fisheries Resources Exploitation, 999 Hucheng Ring Road, 201306 Shanghai, China Introduction X. Chen · B. Liu · J. Li The Key Laboratory of Sustainable Exploitation of Oceanic The purpleback flying squid Sthenoteuthis oualaniensis is Fisheries Resources, Ministry of Education, 999 Hucheng Ring an oceanic species that belongs to the family Ommastre- Road, 201306 Shanghai, China phidae and is distributed in a broad band around the equa- tor from approximately 40°N to 40°S. Its range stretches Y. Chen School of Marine Sciences, University of Maine, Orono, predominately throughout the tropical and subtropical open ME 04469, USA waters of the Indo-Pacific region [1, 2]. Purpleback flying 1 3 Fish Sci squid tend to be concentrated in areas of high primary pro- and growth patterns of squid [24–26]. Beak morphological ductivity, with a patchy distribution observed [3]. characteristics are more reliable than the other hard parts Within this wide distribution, S. oualaniensis is also of squid, as they are large enough to be measured with the known to have a wide ecological range and a complex naked eye and they do not break down in the stomachs of population structure [4]. This structure includes three predators [27, 28]. Beaks have been widely used in taxon- major forms of S. oualaniensis based on differences in omy to identify squid species to family, genus, and species size at maturity [5]: (1) a giant form, mantle length (ML) levels [29–31]. The relationships between beak morpho- 400–500 mm, which occurs only in the northern Indian logical variables and both ML and body weight (BW) have Ocean; (2) a medium form (120–250 mm ML) that occurs been quantified using various models, and these relation- throughout the range of the species; and (3) a dwarf form ships are thought to have the potential to be used for stock (90–120 mm ML) that occurs in equatorial waters. The biomass estimation [32–36]. medium and dwarf forms may also be subdivided into two As it is a feeding organ that tears and bites food, the minor forms on the basis of dorsal photophore and gladius features of different parts of the beak change with the morphology [5]. ontogenetic state of the squid [37]. Another unique char- The total biomass of this squid is thought to be rela- acteristic that has been documented in previous studies is tively high. Nigmatullin et al. [6] previously estimated the the development of darkness or pigmentation in the crest, total stock of S. oualaniensis in the world’s oceans to be lateral wall, or wing of the beak [38–42]. After Hernández- between 8 and 11 million tonnes. Zuev et al. [7] once esti- García [42] defined eight stages of beak pigmentation, the mated the mass of the total stock of S. oualaniensis at 3–4 pigmented part was shown to be related to the stiffness of million tonnes (1.9–2.4 million tonnes for the middle-sized the beak—the tanned parts of the beak are harder than the form) in the Indian Ocean and 5–7 million tonnes in the untanned parts [43, 44]. The development of beak pigmen- Pacific Ocean. This robust species may form joint schools tation is a sign of growth and changes in the diet of the with the similar-sized species Dosidicus gigas and Ommas- squid [42]. trephes bartramii, which have overlapping distributions The objective of the study reported in the present paper [7]. was to use beak growth patterns to estimate the length– At the periphery of the geographical range of S. ouala- weight relationship, sexual maturity stage, and changes in niensis, they are often caught as bycatch by D. gigas and diet, which can be used to help study predator–prey rela- O. bartramii fisheries [2, 8, 9]. Historically, S. oualaniensis tionships involving S. oualaniensis in the tropical Pacific has been commercially fished off Okinawa (in the Ryukyu Ocean. Specifically, the length–weight relationship and Chain), Taiwan (a province of China), and Hawaii by Japa- sexual maturity stage tend to be correlated with distinguish- nese fishing vessels [10]. In 2003, Chinese squid jigging able beak characteristics. Changes in diet were determined fleets began to targetS. oualaniensis in the Indian Ocean using variations in the beak pigmentation of S. oualanien- and landed 5000 t from the northwest Indian Ocean dur- sis. Relating beak characteristics to trophic interactions ing 2003–2005 [11]. In the Pacific Ocean, purpleback fly- permits convenient estimation of the biomass of S. ouala- ing squid are retained as bycatch by fisheries that predomi- niensis using beaks alone in marine mammal research and nately target D. gigas [9, 12]. potentially in fisheries surveys. The growth rate of S. oualaniensis is relatively fast, like those of other oceanic squids; daily food intake is estimated to be about 8–10 % of their total body weight [13]. The Materials and methods broad feeding spectrum of S. oualaniensis will change as the mantle length increases [8, 14]. Amphipods, euphausi- All samples of S. oualaniensis were taken at random from ids, and fish larvae are the main food for juveniles, whereas the catch of the Chinese commercial jigging vessel Puy- adults feed primarily on myctophids and sometimes exhibit uan 802 from April to June 2014. The fishing vessel was cannibalistic behavior [15–17]. S. oualaniensis has been operated in the equatorial waters of the East Pacific Ocean commonly found in the stomachs of various predators such (2°N–5°S and 110°–118°W, Fig. 1). A total of 220 samples as seabirds, large fish, and marine mammals [18–21], and it were collected from this area, comprising 204 females and plays important role in the marine ecosystems of the Indian 16 males. All samples were measured and dissected imme- Ocean and the Pacific Ocean as both a predator and a prey diately after they were landed on deck. Mantle length (ML) species [8, 14, 17]. and body weight (BW) were measured to the nearest 1 mm Hard structures in cephalopods, especially the beak, are and 1 g, respectively. Sex was identified and sexual matu- composites of proteins and chitin fibers [22, 23]. These rity stage was determined by the naked eye based on mor- structures have increasingly been studied in recent years phological changes in the gonads defined by Lipinski and to determine length–weight relationships, age estimates, Underhill [45].