The influence of discharge, photoperiod, and temperature on the reproductive ecology of cyprinids in the Paluxy River, T
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The influence of discharge, photoperiod, and temperature on the reproductive ecology of cyprinids in the Paluxy River, Texas Jeremy T. Munz • Christopher L. Higgins
Received: 24 September 2012 / Accepted: 18 December 2012 / Published online: 4 January 2013 Ó Springer Science+Business Media Dordrecht 2013
Abstract The distributions and abundances of cyprinids in North America are declining at an alarming rate with almost half of all known species considered imperiled and in need of conservation. Much of this loss in biodiversity is a result of flow regulation and climate change, especially in streams in the southern Great Plains that are prone to large and rapid fluctuations in discharge. The overall objective of this study was to examine the influence of discharge, photoperiod, and temperature on the reproductive ecology of cyprinids in the Paluxy River, Texas. Our results support previous findings in that photoperiod and water temperature were influential in the initiation and termination of the annual reproductive season. Interannual differences in GSI for Cyprinella venusta and Notropis volucellus indicated that reproductive effort in certain cyprinids was directly linked to discharge. In 2010, mean gonadosomatic index values for C. venusta (9.60 %) and N. volucellus (9.15 %) were at least twice that of 2011 (4.61 and 3.14 %, respectively); discharge during the spawning season of 2010 averaged 1,965 cfs, whereas it averaged only 177 cfs in 2011. Indeed, yearly differences in streamflow (i.e., mean annual discharge) can significantly
Handling Editor: Thomas Mehner. J. T. Munz C. L. Higgins (&) Department of Biological Sciences (Box T-0100), Tarleton State University, Stephenville, TX 76402, USA e-mail: [email protected]
impact the production of ova in a variety of cyprinids, even those non-broadcast-spawning species such as C. venusta. Consequently, we suggest conservation efforts should focus on maintaining natural flow regimes to combat the overwhelming loss of cyprinid diversity, especially as water extraction and climate change continue to threaten the biodiversity of freshwater fishes. Keywords Gonadosomatic index Reproductive ecology Discharge Cyprinids Streamflow
Introduction The distributions of many freshwater fishes in North America are shrinking and their abundances dwindling. In fact, recent estimates suggest that 39 % of all described species are imperiled (i.e., vulnerable, threatened, or endangered) and in need of conservation (Jelks et al. 2008). The declines in distribution and abundance of these fishes are a result of habitat degradation, pollution, flow regulation and water extraction, fisheries overexploitation, and the introduction of non-native species (Strayer and Dudgeon 2010). Although these factors may not equally contribute to the decrease in biodiversity, they each play a significant role in the decline of certain taxonomic or functional groupings. For example, streamflow has relatively little influence on the abundance of catostomids and percids, whereas it can be very
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