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Authors requiring further information regarding Elsevier’s archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright Author's personal copy Deep-Sea Research I 61 (2012) 123–130 Contents lists available at SciVerse ScienceDirect Deep-Sea Research I journal homepage: www.elsevier.com/locate/dsri Ontogenetic vertical migration of grenadiers revealed by otolith microstructures and stable isotopic composition Hsien-Yung Lin a, Jen-Chieh Shiao a,n, Yue-Gau Chen b, Yoshiyuki Iizuka c a Institute of Oceanography, National Taiwan University, Taipei, Taiwan, ROC No. 1, Sec. 4, Roosevelt Road, Taipei, 10617 Taiwan, ROC b Department of Geosciences, National Taiwan University, Taipei, Taiwan, ROC No. 1, Sec. 4, Roosevelt Road, Taipei, 10617, Taiwan, ROC c Institute of Earth Sciences, Academia Sinica, Nangang, Taipei, Taiwan No. 128, Academia Road, Sec. 2, Nankang, Taipei 115, Taiwan, ROC article info abstract Article history: Otolith d18O and d13C of six species grenadiers were analyzed to reconstruct the historical Received 28 July 2011 residing depths and metabolic activity. During the larval to juvenile stage, Spicomacrurus kuronumai, Received in revised form Hymenocephalus lethonemus, and Bathygadus nipponicus gradually migrated from the mixed layer to the 7 December 2011 thermocline downward over a vertical distance 4140 m after which they moved within a narrow Accepted 10 December 2011 vertical range for the remaining life. The downward migration distance was less than 65 m during the Available online 22 December 2011 larval stage of Hymenocephalus sp. and Coryphaenoides acrolepis, which showed a second descent period Keywords: from the thermocline to deeper water as juveniles. Coryphaenoides marginatus stayed at the lower Grenadiers thermocline during the larval stage and the juveniles migrated downward in a relative short distance Otolith stable isotope around 100 m and settled in deeper water (4600 m), followed by irregular movements over a vertical Ontogenetic vertical migration range of about 200 m during juvenile and adult stages. The otolith d13C profile suggested that fishes Life history (S. kuronumai, H. lethonemus, and B. nipponicus) with a longer migration distance had a higher metabolic rate in their early life-history stages than in the later stages. However, the metabolic rate did not vary for those fishes (H. sp., C. acrolepis and C. marginatus) living within a narrow vertical range during their larval to adult stages. The otolith microchemistry suggested that ontogenetic downward migration was an important strategy for grenadiers linking the life stages between pelagic larvae and benthic settlement. Furthermore, the migration timing and distance for the pelagic larvae varied between species and habitats. S. kuronumai, H. lethonemus, H. sp. and C. acrolepis might metamorphose and settle at the same time, B. nipponicus metamorphosed during migration and C. marginatus migrated as juveniles. & 2011 Elsevier Ltd. All rights reserved. 1. Introduction sea floor and the buoyant eggs float to the thermocline where the larvae are hatched. The larvae grow near the thermocline and Global catches of deep-sea fishes have steadily increased from then descend to adult living depth. Some surveys (Stein, 1980; 2% of the total oceanic catches in 1975 to 33% in 2000 (Garibaldi Endo et al., 1992; Busby, 2005; Fukui and Tsuchiya, 2005; Fukui and Limongelli, 2003). Most deep-sea fisheries take place on et al., 2008, 2010; Endo et al., 2010) of grenadier eggs and larvae continental slopes or seamounts, such as the fisheries for orange agree with the life cycle proposed by Marshall (1973). However, roughy (Hoplostethus atlanticus), black scabbard fish (Aphanopus the early life history is only described for some species of carbo), redfish (Sebastes mentella), blue ling (Molva dypterygia), grenadiers based on limited survey data for certain life stages Greenland halibut (Reinhardtius hippoglossoides), and the grena- (Busby, 2005; Endo et al., 2010). For most grenadiers species, the diers (Cohen et al., 1990; Clark, 2001). available catch records are insufficient to reconstruct their life Nearly all grenadiers are benthopelagic fishes and can be history from larval to adult stage. Therefore, an alternative found in all ocean basins but rarely in the high Arctic. Most method is required to offer robust data for better understanding grenadiers inhabit depths from 100 m to more than 6000 m but the migratory life history of grenadiers. most occur at depths between 200 m and 2000 m (Cohen et al., The otolith is a calcified structure in the inner ears of fishes 1990). Marshall (1973) suggests that grenadiers spawn near the that functions as a part of sensory organ. The periodic formation of growth increments and environmental signals recorded in the otolith serve as a powerful tool for studying life history of n Corresponding author. Tel.: þ886 2 33663227; fax: þ886 2 33663744. teleosts. The otolith increments and checks can provide informa- E-mail address: [email protected] (J.-C. Shiao). tion for daily age determination (Pannella, 1971) and life history 0967-0637/$ - see front matter & 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.dsr.2011.12.005 Author's personal copy 124 H.-Y. Lin et al. / Deep-Sea Research I 61 (2012) 123–130 events such as hatching, settlement and metamorphosis (Hislop nipponicus, Hymenocephalus lethonemus, H. sp., Coryphaenoides et al., 2001; Morioka et al., 2001; Plaza et al., 2001; Hirakawa marginatus, and C. acrolepis were collected in October 2010 off et al., 2007). For deep water fish, the periodic structures in the the southwestern coast of Taiwan by the research vessel ‘‘Ocean otolith including yearly and daily increments have been validated Researcher I’’ (Table 1, Fig. 1). The specimen of H. sp was not by marginal growth analysis (Moku et al., 2001; Swan and intact and morphological characteristics of the remaining carcass Gordon, 2001), radioactive signals (Andrews et al., 1999), tagging only allowed identification to genus name. Hydrological data, (Dougherty, 2008), and rearing (Morales-Nin et al., 2005). Settle- including salinity and temperature, were measured in situ with a ment marks of the otoliths were found in some deep-sea larval or SeaBird Conductivity-Temperature-Depth recorder (SBE 9/11 juvenile fishes such as the greater forkbeard, Phycis blennoides plus, SeaBird Inc., USA, Fig. 2). (Casas and Pineiro, 2000) and greeneye, Chlorophthalmus albatrossis (Hirakawa et al., 2007). Accessory growth centers in otoliths are formed during the larval metamorphosis of 2.2. Otolith preparation Gadiformes (Morales-Nin and Aldebert, 1997), walleye pollock, Theragra chalcogramma (Brown et al., 2001) and ling, Genypterus Sagittal otoliths were dissected from the fish after the mea- blacodes (Morioka et al., 2001). In European hake (Merluccius surement of standard length, preanal length, and weight of the merluccius), accessory growth centers represent larval metamor- grenadiers. Otoliths were embedded in epofix resin (Struers, phosis and settlement on the sea floor (Arneri and Morales-Nin, Demark) and ground on the sagittal plane till the primordium 2000; Morales-Nin et al., 2005). was exposed by the grinding machine (Buehler, Metaserv 2000, The chemical composition of the otolith records environmen- Evanston, IL, USA). Then, the otoliths were polished and treated tal signals and physiological status, which are very useful for with 8% EDTA (ethylene diamine tetra-acetate) for 20–40 s. understanding the autoecology of fishes (Campana, 1999). Otolith Otolith images were taken by a compound microscope (Olympus d18O is influenced by salinity, water d18O values and water BX-51) equipped with a digital camera (DP-71, Olympus) using temperature. The deposition of otolith d18O is in equilibrium reflected and transmitted light. Otoliths were coated with gold with ambient water and the fractionation factor is water tem- and observed under a scanning electron microscope (SEM, JSM- perature dependant (Kalish, 1991; Campana, 1999). Several stu- 6360LV, Japan). The otolith growth increments around the core dies suggest that aragonite d18O is inversely related to the area were interpreted as putative daily increments since they ambient water temperature with a slope of approximately were not validated for these deep-water fishes. A dark and light À0.20 to À0.23 (Grossman and Ku, 1986; Radtke et al., 1998; growth increment was defined as a daily growth increment. Høie et al., 2004), although the intercepts significantly differ The other sagittal otolith of the same fish was prepared in the between species (e.g., Patterson et al., 1993; Thorrold et al., same way as described above for stable isotope analysis. Otolith 1997). Oxygen isotopic composition has been extensively used powders were collected by a computerized micromill (Merchantek, to study natal origin (Shiao