Curtis: Validation of a method for estimating annual fecundity for Hippocampus guttulatus 



331 



Correlates of fecundity 



The influences of body size, water temperature, 

 season, and lunar phase on batch fecundity and 

 reproductive activity (i.e., the proportion of spawn- 

 ing males and females) were investigated. Daily 

 and mean monthly water temperatures in the 

 Ria Formosa were recorded with an Onset HOBO 

 Temperature logger (Onset Computer, Bourne, 

 MA) placed 0.3 m above the substrate on the grid 

 from June 2001 to September 2002. All means 

 are reported with one standard deviation or QS^f 

 confidence intervals (95% CI). Statistical proce- 

 dures were carried out with SPSS 10.0.7 (SPSS 

 Inc., Chicago, IL). 



Results 



Continuous reproduction (CR) model 



Nonlinear regression indicated that the size of 

 male H. guttulatus was a significant predictor of 

 brood size, Z^, which varied from 10 to 567 embryos 

 or juveniles, with a mean of 213.9 ±110.9 (;!=117. 

 caged and dissected males pooled). Both standard 

 length (r^=0.29, P<0.0001, n=117) and wet mass 

 (?-^' = 0.20, P<0.003, n=39) significantly predicted/"^ 

 (Fig. 2). Brood size was not correlated with mean 

 monthly temperature (r-' = 0.00, P=0.90, « =117 1 but 

 was weakly correlated with Julian day in 2001 

 (r2 = 0.06, P=0.015, «=106). 



A total of 4550 records were collected from the 

 553 individually tagged H. guttulatus in 2001 and 

 2002 for an average of 8.2 records per individual 

 (maximum 87). On the grid, 947c of resighted, 

 mature males mated at least once within a cen- 

 sus period. The mean brooding period, ?^, was 

 21.4 (±5.5) days (n = 80 intervals from 73 males, 

 median=20.0 days). Temperature was not a sig- 



^[i..5.5) =0.22, 



nificant predictor of t/^ (r- = 0.004, 

 P>0.05), despite reports of an inverse relationship 

 between temperature and brooding period in other 

 seahorse species (Vincent and Sadler, 1995; Foster 

 and Vincent, 2004). 



The CR model produced the highest estimates 

 of annual spawning frequency, s^ ^,., and realized 

 annual fecundity, /j, ^,.- Assuming continuous re- 

 production from March to October (245 days), male H. 

 guttulatus was predicted to produce 11.5 broods annu- 

 ally. Mean annual fecundity was estimated as approxi- 

 mately 2450 young per year (Table 1). 



Intermittent reproduction (IR) model 



The interbrood interval, f,^, ranged from to 61 days 

 and had a mean of 12.9 (±8.2) days (/! = 98 intervals 

 from 58 males; median = 10.5 days) (Table 1). Size 

 did not influence the number of broods produced by 

 males during the census periods (Kruskal-Wallis test, 



600 n 



500 



400 



300 



200 



100 







• •• 







400 



10 12 14 16 18 20 



Standard length (cm) 



B 



22 



300 



200 



100 



% • 



10 



12 



14 



Wet mass (g) 



Figure 2 



Relationship between Hippocampus guttulatus (long-snouted 

 seahorse) male size and brood size (solid circles represent 

 embryos dissected from brood pouches, open circles represent 

 live juveniles born in cages): (A) standard length (n = 117), 

 and (B) wet mass (n = 40). Equations of the fitted line in (A) 

 and (B) are y=18.7e" '"'' and y=104.3e'' o^", respectively. Open 

 triangles in (A) represent mean clutch sizes of female Hippo- 

 campus guttulatus in 12 length classes (Americano, D. 2004. 

 Aspects of the reproductive biology of Hippocampus guttulatus 

 (Cuvier, 1829) [In Portuguese], Undergraduate thesis, 51 p. 

 Universidade do Algarve, Faro, Portugal.) 



X^ = 3.0, n=73, df=5, P=0.7) and temperature was not 

 a significant predictor of <,j (r- = 0.001, F[j9-] = 0.07, 

 P=0.79). Incorporating f,^ into the IR model led to 

 substantially lower estimates of spawning frequency 

 and annual fecundity than predicted by the CR model: 

 7.14 (±4.89) broods per year and 1527 (±1309) young 

 per year, respectively (Table 1). 



All resighted, mature females prepared at least one 

 clutch of eggs within a census period on the grid. The 

 mean number of days females had hydrated eggs, t^, 

 was 2.58 (±2.66) days (n=72 inferred clutches), indicat- 

 ing that females required at least 2.5 days to prepare 



