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Fishery Bulletin 105(3) 



or clutch predation fWeddle and Burr, 1991; Cole and 

 Sadovy, 1995). Such estimates of "potential" annual 

 fecundity are usually difficult to validate because of 

 the challenges of monitoring early life history stages 

 (e.g., eggs, embryos, larvae) over time and space. In 

 many species that provide parental care, however, 

 both mating and brooding may be directly observed 

 (e.g., Vincent and Giles, 2003). Such species provide 

 an opportunity to validate indirect inferences based 

 on egg production and to obtain more accurate esti- 

 mates of the actual number of young produced (e.g.. 

 Cole and Sadovy, 1995). Seahorses are asynchronous, 

 indeterminate multiple spawners that provide obligate 

 paternal care in a sealed brood pouch (Boisseau, 1967; 

 Wallace and Selman, 1981). Although numerous stud- 

 ies have investigated aspects of seahorse reproductive 

 behavior (e.g., Vincent and Sadler, 1995; Perante et 

 al., 2002), annual fecundity has been estimated for 

 only one wild seahorse population (White's seahorse. 

 Hippocampus whitei, Vincent and Giles, 2003) by di- 

 viding the duration of the reproductive season by the 

 brooding period (time required for a male to brood 

 a clutch of eggs), and multiplying this estimate of 

 spawning frequency by the average brood size (i.e., 

 batch fecundity). Implicit in this method are three as- 

 sumptions: 1) the time between release of young and 

 remating is negligible, an assumption that was sup- 

 ported by observations of rapid remating in H. whitei 

 (Vincent and Sadler, 1995), 2) individuals reproduce 

 continuously from the beginning until the end of the 

 reproductive season, and 3) there is no variation in 

 brood size (a potentially unrealistic assumption, Vin- 

 cent and Giles [2003]). If validated, this method could 

 be used to estimate the realized annual fecundity of 

 several Hippocampus spp. (lUCN^) with data that 

 already exist (Foster and Vincent, 2004). 



In this article, I used European long-snouted sea- 

 horses (Hippocampus guttulatus) (Cuvier, 1829), to 

 validate three progressively realistic models for esti- 

 mating spawning frequency and realized annual fecun- 

 dity. The objectives of this study were 1) to estimate 

 the batch fecundity and spawning frequency of//, gut- 

 tulatus, 2) to identify correlates of fecundity, and 3) to 

 evaluate the predictive accuracy of the three models. 

 The simplest model is the calculation employed by 

 Vincent and Giles (2003). The second model includes 

 an estimate of interbrood interval. The most realistic 

 model is a generalization of the "spawning fraction" 

 method (Hunter and Leong, 1981) that could be applied 

 nondestructively to estimate realized annual fecundity 

 in species of conservation concern. The study objectives 

 were addressed by using fishery-independent sampling 

 and underwater visual census in a locally abundant 

 and unexploited population of H. guttulatus. 



Materials And Methods 



Species description 



The life history and ecology of seahorses has been 

 reviewed by Foster and Vincent (2004). Hippocampus 

 guttulatus inhabits seagrass- and macroalgae-dominated 

 communities in the Mediterranean Sea and the north- 

 eastern Atlantic Ocean (Lourie et al., 1999). Individuals 

 begin reproducing at approximately 1 year of age and 

 live 4 to 5.5 years (Boisseau, 1967; Curtis and Vincent, 

 2006). Adults range in size from 110 to 210 mm standard 

 length (sum of head, trunk, and tail lengths, Lourie 

 et al., 1999) and from 2.4 to 22.5 g wet mass (Curtis 

 and Vincent, 2006). Male and female seahorses mate 

 monogamously within reproductive cycles: the female 

 deposits an entire clutch of eggs into the male's brood 

 pouch (Jones et al., 1998). Brooding male H. guttulatus 

 (i.e., with full pouches) have been captured from March 

 to October (Boisseau, 1967; Reina-Hervas, 1989) and 

 in January (Lo Bianco, 1888). The ovarian structure of 

 H. guttulatus indicates that females produce multiple 

 clutches per year (Boisseau, 1967). 



Sampling 



This study was carried out in the Ria Formosa lagoon in 

 southern Portugal (36°59'N, 7°51'W). The Ria Formosa 

 is a shallow, productive coastal lagoon characterized by 

 high water turnover rates, seagrass beds, sand flats, salt 

 marshes, and a network of channels and tidal creeks 

 (Machas and Santos, 1999; Curtis and Vincent, 2005). 

 Data employed in this study were derived from fisher- 

 ies-independent samples of fish community structure 

 (Erzini et al.^) and from underwater visual censuses of 

 tagged H. guttulatus on a small focal study site (Curtis 

 and Vincent, 2006). Seahorses captured during fisher- 

 ies-independent sampling were collected monthly from 

 September 2000 to July 2002 (except January 2002) 

 at 53 stations throughout the western part of the Ria 

 Formosa lagoon by using small beach seines, push nets, 

 or beam trawls (Erzini et al.^), and then frozen. Data 

 from all the captured seahorses were opportunistically 

 recorded and included the standard length, life history 

 stage, sex, reproductive state, wet mass, and brood 

 size of males with full pouches (details provided in 

 Curtis, 2004; Curtis and Vincent, 2006). Brood sizes 

 were obtained by dissecting the full pouches of cap- 

 tured males and counting all of the developing embryos. 

 Broods with embryos captured during the earliest stages 

 of development (<stage 10, sensu Boisseau, 1967) were 



lUCN (World Conservation Union). 2006. 2006 lUCN 

 Red List of Threatened Species. lUCN Species Survivial 

 Commission, 219c Huntingdon Road, Cambridge CB3 ODL, 

 United Kingdom. Website: http://www.redlist.org (accessed 

 31 May 2006). 



2 Erzini, K., L. Rentes, R. Coelho, C. Correia, R G. Lino, P. 

 Monteiro. J. Ribeiro. and J. M. S. Gonfalves. 2002. Re- 

 cruitment of sea breams (Sparidae) and other commercially 

 important species in the Algarve (southern Portugal). Final 

 Report, 178 p. Commission of the European Communities 

 DG XIV/C/1. Directorate-General for Fisheries and Maritime 

 Affairs, Unit for Information and Communication, European 

 Commission, B-1049, Brussels, Belgium. 



