Life history and ecology of seahorses: implications for conservation and management

Abstract

We present the first synthesis of the life history and ecology of seahorses, compare relationships for seahorses with other marine teleosts and identify research needs. Seahorses occurred primarily amidst temperate seagrasses and tropical coral reefs. Population densities were generally low, ranging from 0 to 0Á51 individuals m À2 , but reached 10 m À2 in some patches. Inferred life spans ranged from 1 to 5 years. Seahorses consumed live prey and possibly changed diet as they grew. Growth rates are poorly investigated to date. Reproduction and mating systems are the best-studied aspects of seahorse ecology. The relationship between size at first maturity and maximum size in seahorses conformed to that for other marine teleosts. All seahorse species were monogamous within a cycle, but some were polygamous across cycles. Direct transfer of clutches to the brood pouch of the male fish made it difficult to measure clutch size in live seahorses. After brooding, males released from c. 5 to 2000 young, depending on species and adult size. Newborn young measured from 2 to 20 mm in length, which was a narrower size range than the 17-fold difference that occurred in adult size. Newborn body size had no relationship to adult size. Both eggs and young were larger than expected among marine teleosts, even when considering only those with parental care, but brood size at release was lower than expected, perhaps because the young were more developed. The size of adults, eggs and young increased with increasing latitude, although brood size did not. Considerable research is needed to advance seahorse conservation and management, including (a) fisheriesdependent and fisheries-independent abundance estimates, (b) age-or stage-based natural and fishing mortalities, (c) growth rates and age at first maturity, and (d) intrinsic rates of increase and age-or size-specific reproductive output. Current data confirm that seahorses are likely to be vulnerable to high levels of exploitation. # 2004 The Fisheries Society of the British Isles

Structure and mechanical properties of selected protective systems in marine organisms

“…Unlike most fish, seahorses swim upright, utilizing their dorsal fin for propulsion and two pectoral fins for maneuverability, resulting in slow swimming velocities [147][148][149]. Thus, they use their prehensile tails for stability, gripping and holding onto objects such as sea grasses, mangrove roots, and coral reefs [147]. The tail skeleton is composed of several articulating segments arranged into cross-sectional squares, each composed of four bony plates that surround a central vertebra (Fig.…”

“…The tail skeleton is composed of several articulating segments arranged into cross-sectional squares, each composed of four bony plates that surround a central vertebra (Fig. 17b) [147][148][149][150][151][152][153][154]. These plates are connected by overlapping joints that allow them sufficient flexibility for grasping as well as added strength for armored protection [154].…”

The life history of weedy seadragons, Phyllopteryx taeniolatus (Teleostei:Syngnathidae)

“…The family Syngnathidae includes the seahorses, pipefishes and seadragons, a unique group of small cryptic fishes found worldwide in coastal temperate and tropical waters (Foster and Vincent 2004). Aside from their unique appearance, syngnathids are characterised by their reversed sex roles in which the male incubates eggs received from the female in a brood pouch located on the trunk (seahorses) or on a brood patch on the underside of the tail or abdomen (pipefishes and seadragons) (Herald 1959).…”

“…Aside from their unique appearance, syngnathids are characterised by their reversed sex roles in which the male incubates eggs received from the female in a brood pouch located on the trunk (seahorses) or on a brood patch on the underside of the tail or abdomen (pipefishes and seadragons) (Herald 1959). As a result, offspring survival is dependent on paternal investment (Foster and Vincent 2004). In addition, syngnathids produce relatively few young and tend to have low population densities, making them susceptible to overexploitation (Foster and Vincent 2004).…”

“…As a result, offspring survival is dependent on paternal investment (Foster and Vincent 2004). In addition, syngnathids produce relatively few young and tend to have low population densities, making them susceptible to overexploitation (Foster and Vincent 2004). Significant markets have developed for both dead and live animals, particularly seahorses, for curios, traditional medicines and aquarium displays (Salin et al 2005).…”