Age, Growth, and Mortality of Lane Snapper from Southern Florida

Rings on sectioned otoliths were used to determine ages of lane snapper, Lutjanlis synagris, sampled from the south Florida headboat and commericial handline and trap fisheries. Rings were identified and counted on 76% of the otoliths examined, and measurements were made on 61%. The oldest fish encountered was 10 years and 512 mm TL. Back-calculated mean lengths at annulus formation were 135, 196, 233, 261, 285, 310, 338, 367, 411 and 426 mm TL for age groups 1 to 10, resNectively. The von Bertalanffy equation describing theoretical ~rowth wasQ 1 = 501 (160 · 133 (I+ 1 ·~. The length-weight rei a· tionship was W = 0.000102TL ·• The relationship of fork length to total length was TL = -2.6252 + 1.0891 FL. Lane snapper were fully recruited to the hook·and·line fishery as 5 year old fish. A Beverton and Holt yield·per-recruit model suggests a maximum yield· per-recruit of 500 g when instantaneous fishing mortality was 0.5 and recruitment ages were 1.5 to 3.0 years. The lane snapper, Lutjanus synagris, known in Latin America as Pargo biajaiba and Dibujo de una biajaiba, is a tropical and warm temperate marine fish, which commonly occurs in the western Atlantic from the northern coasts of Florida to southeastern Brazil and is often reef associated. Occasionally, juveniles are found as far north as North Carolina as a result of Gulf Stream transport of eggs and larvae and are probably not indicative of local, established populations. The habitat of adults is highly variable. It includes irregular substrates such as coral reefs, rock outcroppings, and shipwrecks offshore, and smooth bottom usually associated with seagrass beds and mangrove thickets inshore. Larger individuals generally occur offshore, smaller fish are found in estuaries and coastal waters (Starck and Schroeder 1971) . Like other iutjanids, the lane snapper is important to both recreational and commercial fisheries. The species is 109 common throughout its range and is caught by hook-and-line, beach seines, fish traps, and trawls. Recreational anglers fish for reef fish from headboats or smaller private boats, using manual or electric reels, sturdy boat rods, heavy monofilament line, and two-hook bottom rigs baited with squid or cut fish (Huntsman 1976). This form of deep water fishing is very popular off Florida where the lane snapper is caught along with mutton snapper, Lutjanus ana/is, gray snapper, L. griseus, red snapper, L. campechanus, and yellowtail snapper, Ocyurus chrysurus, as well as grunts (Haemulidae), groupers (Serranidae), and porgies (Sparidae). Smaller reef fish, including young lane snappers, are caught by anglers fishing from piers, jetties, bridges, and the shore. Three previous studies have been published on the age and growth of lane snapper (Rodriguez Pino 1962; Alegria and Menezes 1970; and Claro and Reshetnikov 1981). However, all three were primarily directed at small (young) 1 Manooch and Mason: Age, Growth, and Mortality of Lane Snapper from Southern Florida Published by The Aquila Digital Community, 1984 110 C. S. Manooch, Ill and D. L. Mason . fish, hence the data are only marginally useful in calculating growth parameters needed to derive harvest strategy,models for the fishable stock(s) off Florida. Our research was part of the National Marine Fisheries S'ervice, Southeast Fisheries Center's continuing major research program on reef fisheries. Special appreciation . is exterded to Robert L. Dixon, Beaufort Laljloratory, and Harold Brusher, Panama City Laboratory, who directed field sampling activities along the east coast of Florida and in the Florida Keys, respectively. The objectives of this study were to: 1) determine the age structure and growth rates of lane snapper. in south Florida, 2) estimate total inst~ntaneous mortality rates from catch curves derived from recreational headboat catches, and 3) construct a yield-per-recruit·model to demonstrate the effects of ~ifferent levels of fishing and recruitment age on potential yields. Such information is needed by various regional :Fishery Management Councils for preparing reef fishery management plans as provided for under the Fishery Conservqtion and Management Act of 1976.