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Document Type:Latin Dissertation
Language of Document:English
Record Number:55248
Doc. No:TL25202
Call number:‭1450055‬
Main Entry:Sara Joy Tripp
Title & Author:Understanding how harvest influences the life history and demographics of shovelnose sturgeon in the middle Mississippi RiverSara Joy Tripp
College:Southern Illinois University at Carbondale
Date:2007
Degree:M.S.
student score:2007
Page No:62
Abstract:Shovelnose sturgeon Scaphirhynchus platorynchus in the Middle Mississippi River is one of the last commercially viable sturgeon populations in the world. To determine whether commercial harvest of the black-egg (sexually mature) females is impacting this population, information regarding sex-specific demographics and the reproductive life history is required. Adult shovelnose sturgeon were sampled using gill nets (5-cm bar mesh) monthly during February 2005 through July 2006 at three sites on the Middle Mississippi River between Cairo, IL and St. Louis, MO; (RKM: 201-198; 191-188, and RKM 127-124). Of all shovelnose sturgeon sampled, 363 were females and 416 were males, deviating from 1:1 (p=0.06). Sex-specific length frequency distributions differed (p=0.03) with females having a larger median fork length (614 mm). Compared to historical data, the population shifted towards longer fish, and somatic growth declined. The population also shifted towards older fish with reduced recruitment. Age at maturity was later than previously reported, with females maturing at a mean age of 10.5 years and males at 9 years of age. Total egg count was slightly lower than previously reported with a mean of 29,573/female. However, the spawning cycle had not changed with most males and females spawning every 2 and 3 years, respectively. Larval sturgeon were also sampled to link age at maturation, timing and periodicity of spawning, and larval growth rates. Larval sturgeon occurred during June and July of 2005 and May and June of 2006, confirming successful spawning. Larval sturgeon grew between 0.69 to 1.69 mm total length per day among four distinct cohorts produced each year. For the first time for this population, sturgeon were found to spawn during the fall. Fall sturgeon contained ripe eggs with polarization indexes (PIs) <0.05; larval sturgeon were collected thereafter. The population structure is changing likely due to increased commercial harvest perhaps coupled with poor habitat conditions. The life history strategy, which is similar to other sturgeon, likely places this species at risk of overharvest.
Subject:Biological sciences; Larval sturgeon; Middle Mississippi River; Population demographics; Shovelnose sturgeon; Sturgeon aging; Ecology; Organismal biology; 0329:Ecology; 0472:Organismal biology
Added Entry:J. E. B. Garvey, Brooks M.
Added Entry:Southern Illinois University at Carbondale