SIZE-SPECIFIC LIFE-HISTORY PATTERN OF A SHALLOW-WATER GORGONIAN

Size, rather than age, may be a more reliable indicator of survivorshi p and growth in colonial coral reef organisms. This study examined the size-specific demography of the shallow-water gorgonians Pseudopterog orgia spp. from 1984 to 1992 in Puerto Rico. Size-specific survivorshi p patterns were well-defined. Average (median) survivorship for large colonies (>10 cm tall) was relatively high (96.5%.yr(-1)) and constant (range: 91.8-100%.yr(-1)) while survivorship for small colonies (<6 c m tall) was low (62.0%.yr(-1)) and variable (range: 53.1-85.4%.yr(-1)) . Growth rates were largely unrelated to colony size; about 47% of col onies of all sizes grew into larger size classes per year. However, a significant positive relationship between survivorship and growth of s mall, but not large, colonies suggests an indirect size-specific growt h effect. No strong age-specific effects were evident for colonies of equivalent sizes. Size-based population matrix models indicated that t he combination of (1) low and variable survivorships of small colonies , and (2) high and constant survivorships of large colonies, lead to e pisodic variations in Pseudopterogorgia populations. The size-specific demography of Pseudopterogorgia can be viewed as an analog to the ''b et-hedging'' interpretation of life history pattern.