Age, Growth, and Mortality of Spotted Seatrout in Florida Waters

Abstract

Estimates of age, growth, and mortality of spotted seatrout Cynoscion nehulosus were made by analyzing fish from commercial and recreational catches in 1986-1988 in three estuarine areas of Florida: Apalachicola Bay, Charlotte Harbor, and Indian River Lagoon. Thin sections of sagittae were used to determine age: annulus formation occurred in November-May. The maximum observed age differed among areas, ranging from 5 to 9 years for males and from 6 to 8 years for females. Spotted seatrout reached 301-337 mm total length at the end of their first year. Females were generally larger at age than males, although growth was highly variable. After age 1, male growth slowed to an average of 34-51 mm/year and was modeled best by area-specific linear growth equations. Females showed asymptotic growth that slowed from 87-107 mm at ages 1-2 to 46-60 mm at ages 4-5 and that was modeled best by area-specific Gompertz growth equations. Males and females from Indian River Lagoon and Apalachicola Bay were generally larger than those from Charlotte Harbor. Males were heavier than females of the same length. Estimates of total annual mortality were 48-76% in 1986-1988 and seemed highest in Apalachicola Bay. Patterns of growth did not reflect those previously used to support hypothesized divisions of spotted seatrout into separate subpopulations in Florida estuaries. Differences in growth and age composition observed among estuaries may reflect differences in environmental and fishing effects rather than genetic differentiation among estuaries. MethodsSpotted seatrout were sampled monthly from commercial and recreational catches during

Age and Growth of Sand Seatrout (Cynoscion arenarius) in the Estuarine Waters of the Eastern Gulf of Mexico

“…Spotted seatrout from Florida demonstrated much faster growth (Murphy and Taylor 1994) than we found for sand seatrout. Spotted seatrout length at age 1 yr ranged from about 100 mm to nearly 200 mm greater than sand seatrout at age 1 yr, depending upon the sex of the fish and the estuary sampled.…”

“…Length-atage of sand sea trout was quite variable between individuals, but within the limits previously ITported for this species (Shlossman, 1980). Other closely related species, such as spotted seatrout (Murphy and Taylor, 1994) and weakfish (Lowerre-Barbieri et al, 1995), have also shown great variability at age. The protracted spawning period that these species have has been recognized as a factor contributing to wide variability in length-at-age (Lowerre-Bar-bieri eta!., 1995).…”

“…The percentage of marginal increment was calculated as the distance between the final annulus and the otolith margin divided by the outermost interannulus distance (Crabtree eta!., 1996). Age was estimated based upon annulus count, percentage of marginal increment, timing of annulus formation, capture date for each fish, and median hatch date (LowerreBarbieri et a!., 1994; Murphy and Taylor, 1994). Use of a Jan. 1 hatch date resulted in unrealistic length-at-age estimates.…”

Regional variation in the life history of the canary drum Umbrina canariensis (Sciaenidae), in South African waters

“…Unfortunately nearly all published studies on sciaenid age and growth have reported percentage agreement as a measure of ageing precision. Published values of percentage agreement for temperate and subtropical sciaenids are: 88-99.8% for Cynoscion nebulosus (Murphy and Taylor, 1994;Nieland et al, 2002), 99-100% for Cynoscion regalis (Lowerre- Barbieri et al, 1994), 99% for Micropogonias undulatus , 90-92% for Micropogonias furnieri (ManickchandHeileman and Kenny, 1990), 92% for Pogonias cromis (Beckman et al, 1990), and 96-100% for Sciaenops ocellatus (Beckman et al, 1988;Murphy and Taylor, 1990;Ross et al, 1995;Murphy and Crabtree, 2001). Percentage agreement for the sectioned otoliths of U. canariensis used in this study was substantially less than these reported values, only, 43% agreement between the first and second reading rising to 80% agreement between the second and third reading.…”

Sex-Specific Movement Response of an Estuarine Sciaenid (Cynoscion nebulosus) to Freshets

“…First, female spotted seatrout experience high total mortality rates (67-75 % annually) because recreational anglers target larger (female) fish (Murphy and Taylor 1994;Nieland et al 2002). Therefore, by the end of each freshet period or 6-12 months post-release, only a portion of the 12-33 females released during each tagging event remained alive and available for detection.…”