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Collection, Age, Growth, and Population Attributes of Triploid Grass Carp Stocked into the Santee‐Cooper Reservoirs, South Carolina
Author(s) -
Morrow James V.,
Kirk James P.,
Killgore K. Jack
Publication year - 1997
Publication title -
north american journal of fisheries management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.587
H-Index - 72
eISSN - 1548-8675
pISSN - 0275-5947
DOI - 10.1577/1548-8675(1997)017<0038:cagapa>2.3.co;2
Subject(s) - hydrilla , biology , fishery , grass carp , zoology , hectare , population , fish <actinopterygii> , ecology , demography , aquatic plant , sociology , macrophyte , agriculture
Collection techniques were developed for monitoring populations of triploid grass carp Ctenopharyngodon idella stocked into the Santee‐Cooper reservoirs, South Carolina, to control hydrilla Hydrilla verticillata . Skilled bowfishers, who were paid a bounty of US$50.00 per fish, collected 69, 125, and 160 triploid grass carp in 1992, 1993, and 1994, respectively. Fish were fully vulnerable to bowfishing by age 2. Examination of sectioned utricular otoliths (lapilli) revealed annual marks formed during May–June. Weight ( W ) increased linearly with age ( t , years), for ages 1–6; W = −2,360 + 3,016 t . Age‐specific weights ranged from 0.39 kg to 15.68 kg for fish of ages 1–6. The weight to total length (TL, mm) relation varied little during the study and was W = 0.425(TL) 3.185 . A von Bertalanffy growth equation was fitted to describe the relation between length and age. TL t = 1,044(1 – e –0.615( t − 0.590) ). The annual rate of mortality was 22% in 1994. We estimate that 350,000 triploid grass carp, weighing about 2,000,000 kg, were present in the system as of August 1994; this represented approximately 17 grass carp, or 97 kg, per vegetated hectare. Collection and aging techniques developed in this study may have application in places where triploid grass carp are conservatively and incrementally stocked into large systems. In this regard, population density and growth can be monitored and future stockings adjusted accordingly.