Population demographics of Hickory Shad (Alosa mediocris) during a period of population growth

Abstract

Abstract-Our study goal was to characterize the demographics of the population of Hickory Shad (Alosa mediocris) in the Albemarle Sound-Roanoke River watershed during a period of population increase and to assess its susceptibility to harvest. Adults were collected from gillnet surveys and a river recreational fishery from February to May 1996. The male-to-female ratio was similar between the Albemarle Sound (0.73:1) and the spawning grounds in Roanoke River (0.76:1). Ages were 2-7 years, but most sampled fish were age 3 or 4. The von Bertalanffy growth equation was L t = 460 (1 -e −0.24(t + 1.63) ), where L t was predicted length at time t for sexes combined. Total mortality (Z) was 1.43 for males age 3-5, 1.76 for females age 4-6, and 1.40 for sexes combined. Sexual maturity in both sexes was essentially complete by age 4. Repeat spawning was common: 46.8% of males were virgin, 45.5% had spawned once, and 7.7% had spawned 2 or 3 times. For females, 24.9% were virgin, 45.5% had spawned once, and 29.6% showed evidence of spawning 2, 3, or 4 times. Mesentery fat in both sexes decreased from the prespawning aggregation (staging) area in the sound to the river spawning grounds, indicating that both sexes feed extensively in ocean waters before the inland portion of the spawning migration. The short lifespan of Hickory Shad, combined with an early age to maturity and an anadromous migration pattern, indicates that mature individuals are very susceptible to recreational and commercial harvest and are removed by exploitation or natural mortality within 1 or 2 seasons.

Variations in reproduction and age structure in the North American river otter in North Carolina, USA

“…Also, we detected breeding in juvenile and yearling otters, in a naturally recovered population (Piedmont FMU), and in a population that has been stable for decades (Coastal Plain FMU). Abundant resources contribute to reproduction and fish abundance, in general, has improved throughout our study (Rulifson and Batsavage 2014, Lynch et al 2016), but it does not fully explain why we failed to detect juvenile and yearling reproduction during the 1970s.…”

Exceptional longevity in a lightly exploited, semi‐anadromous clupeid (Perth herring Nematalosa vlaminghi) within a degraded estuarine environment

“…In general, ageing of fish from otolith increments is more accurate and precise than that from scale increments (Beamish & McFarlane, 1983; Campana, 2001; Maceina et al ., 2007). Scale‐based methods were historically used to age anadromous clupeids, but these methods can underestimate the age of older fish by several years compared to otolith‐based methods (Duffy et al ., 2012; Elzey et al ., 2015; Harris et al ., 2007; LaBay & Lauer, 2006; Rulifson & Batsavage, 2014; Schlick & de Mutsert, 2019). Chubb and Potter (1986) reported difficulties in reading the scales of N. vlaminghi older than 5 years, so some of these fish may have been underaged.…”

Alewife and Blueback Herring Captured by Intertidal Weirs of the Inner Bay of Fundy, Canada, Display Seasonal Demographics that Suggest Multiple Migrating Stocks

“…After migrating through Cobequid Bay during July and August, fat levels in American Shad declined to an average of 16.3%. Studies on another alosine, the Hickory Shad A. mediocris , indicated that peritoneal fat deposits were greatest just prior to fish entry into estuarine waters but declined during the upstream spawning migration (Murauskas and Rulifson 2011; Rulifson and Batsavage 2014). Condition factors and peritoneal fat deposits began to increase during the postspawning migration downstream toward marine waters.…”