327 



Abstract — The long-snouted seahorse 

 (Hippocampus guttulatus) (Cuvier. 

 18291. was used to validate the pre- 

 dictive accuracy of three progressively 

 realistic models for estimating the 

 realized annual fecundity of asyn- 

 chronous, indeterminate, multiple 

 spawners. Underwater surveys and 

 catch data were used to estimate the 

 duration of the reproductive season, 

 female spawning frequency, male 

 brooding frequency, and batch fecun- 

 dity. The most realistic model, a gen- 

 eralization of the spawning fraction 

 method, produced unbiased estimates 

 of male brooding frequency (mean 

 ±standard deviation [SD] = 4.2 ±1.6 

 broods/year). Mean batch fecundity 

 and realized annual fecundity were 

 213.9 (±110.91 and 903.6 (±522.4), 

 respectively. However, females pre- 

 pared significantly more clutches 

 than the number of broods produced 

 by males. Thus, methods that infer 

 spawning frequency from patterns in 

 female egg production may lead to 

 significant overestimates of realized 

 annual fecundity. The spawning frac- 

 tion method is broadly applicable to 

 many taxa that exhibit parental care 

 and can be applied nondestructively 

 to species for which conservation is 

 a concern. 



Validation of a method for estimating 



realized annual fecundity in a multiple spawner, 



the long-snouted seahorse 



{Hippocampus guttulatus), 



using underwater visual census 



Janelle M. R. Curtis 



Email address: j.curtls(S)flshenes.ubc.ca 



Department of Biology 



McGill University 



1205 Dr Penfield Avenue, Montreal 



Quebec, Canada H3A 1B1 



Present address: Project Seahorse 



FIshenes Centre 



University ol British Columbia 



2202 Mam Mall, Vancouver 



Bntish Columbia, Canada V6T 1Z4 



Manuscipt submitted: 27 April 2006 

 to the Scientific Editor's Office. 



Manuscript approved for publication 

 25 October 2006 by the Scientific Editor. 



Fish. Bull. 105:327-336 (2007). 



Reliable estimates of fecundity for 

 multiple spawning fishes are difficult 

 to obtain because of the logistic chal- 

 lenges associated with monitoring the 

 reproductive activity of mature indi- 

 viduals over extended periods of time 

 (Parrish et al., 1986). Fecundity esti- 

 mates require knowing the number of 

 young produced per spawning event 

 (batch fecundity), as well as the 

 number of batches of young produced 

 per year (annual spawning frequency) 

 (Hunter et al., 1986; Lowerre-Barb- 

 ieri et al., 1996). Consequently, esti- 

 mates of annual fecundity for multiple 

 spawners often are derived from the 

 sampling of ovaries to evaluate tem- 

 poral patterns in the development and 

 maturation of oocytes (Hunter and 

 Leong, 1981; Murua and Saborido- 

 Rey, 2003). However, the reliability 

 of histological assessments is limited 

 for estimating the annual fecundity 

 of fishes with asynchronous oocyte 

 development and indeterminate 

 recruitment (e.g., anchovies, Engrau- 

 lis spp.) (Brown-Peterson et al., 1988, 

 Murua and Saborido-Rey, 2003). In 

 these fishes, no one cohort of oocytes 

 is dominant, and yolked oocytes form- 

 ing new clutches are recruited from 

 previtellogenic stages on a continual 

 basis throughout the reproductive 

 season (Wallace and Selman, 1981). 



To obtain estimates of annual fecun- 

 dity in asynchronous, indeterminate 

 spawners, batch fecundity and spawn- 

 ing frequency are estimated by using 

 different approaches. Batch fecundity 

 can be obtained directly from the 

 number of eggs released per spawning 

 event or from the number of hydrated 

 eggs present in the ovary immedi- 

 ately before spawning. Spawning fre- 

 quency can be obtained indirectly by 

 using a plot of the fraction of females 

 spawning (indicated by the presence 

 of hydrated eggs or new postovula- 

 tory follicles in the ovaries) over time 

 (spawning fraction method. Hunter 

 and Leong, 1981; Murua and Sabo- 

 rido-Rey, 2003). 



Estimates of annual fecundity 

 based on the number of eggs pro- 

 duced per year are reliable provided 

 populations are sampled adequately 

 and appropriately (DeMartini and 

 Fountain, 1981; Hunter and Leong, 

 1981), and egg production is an un- 

 biased proxy for the actual number 

 of offspring produced. Histological 

 methods for estimating annual fe- 

 cundity may overestimate the actual 

 number of young produced, or real- 

 ized annual fecundity, if estimates 

 do not correct for losses due to atre- 

 sia, inability of females to secure 

 mates, low fertilization efficiency, 



