Freshwater Turtles: Misconceptions and Commercial Collection

Texas map turtle, Colorado River, Travis County, Texas (Cullen Hanks).
Texas map turtle, Colorado River, Travis County, Texas (Cullen Hanks).

Freshwater turtles are a conspicuous component of freshwater ecosystems in Texas. Habitat loss and degradation, competition with non-native species, commercial collection (currently legal for only four freshwater turtle species in Texas), depredation by landowners and fishermen, and vehicle mortality represent significant threats to turtle populations.  Some of these threats are not unique to turtles and, in fact, apply to many species.

Misconceptions

Other threats are the result of misconceptions about the role of freshwater turtles in natural environments and a consequential undervaluing of these reptiles as components of healthy ecosystems.  This prejudice, in turn, has paved the way for indiscriminate culling and collection of turtles across Texas.  Turtles are particularly susceptible to decline due to their slow growth rates and low survivorship to adulthood.  In addition, large female turtles are responsible for the majority contribution to annual reproduction yet typically make up only a small percentage of wild populations and are disproportionately impacted by commercial harvest and road mortality.  Turtle populations may take decades to recover from declines.

Many landowners and fishermen express dislike for turtles because of the perceived notion that they prey on- or compete with- game fish, including largemouth bass and catfish.  In fact, freshwater turtles are primarily omnivorous with a majority of their diet composed of aquatic plants, mollusks, and crustaceans.  Even notorious carnivores such as softshell turtles and the common snapping turtle primarily feed on vegetation and invertebrates, along with some carrion.

Red-eared slider, Estero Llano Grande State Park, Hidalgo County, Texas (Cullen Hanks).
Red-eared slider, Estero Llano Grande State Park, Hidalgo County, Texas (Cullen Hanks).

Species such as the red-eared slider and Texas river cooter are more carnivorous as juveniles but transition to a largely vegetarian diet by the time they reach a few inches in length (Dreslik 1999).  Fish, even small species such as minnows, make up a relatively small part of their diet.  Turtles are often blamed for eating fish and stealing from trotlines but this is due largely to the fact that turtles do not discriminate between carrion on a hook or floating freely.

Disdain for turtles has often led landowners to trap or shoot turtles in private ponds in the hope that removing turtles would aid fish populations.  Recent research has documented the important role turtles play in the structure and stability of aquatic food webs and ecosystem processes (Aresco 2009).  Indeed, turtles may improve fishing conditions by helping to break down organic material (thus, freeing it up for consumption by aquatic invertebrates which become prey for turtles and fish alike) and consuming aquatic vegetation (Lindsay 2013).

Commercial Collection

Variety of turtles for sale in Chinese market (Vmenkov).
Variety of turtles for sale in Chinese market (Vmenkov).

The impact of commercial harvest on global turtle populations has been well-documented and represents a significant threat to the survival of many turtle species (Gibbons et al. 2000, Mali 2014).  Steep population declines and extirpations of many Asian turtle species due to harvest pressures have led to increased export of turtle species from the United States to meet market demands.  Slow growth rate, long generation time, and targeting of large, breeding age females for collection make turtles particularly susceptible to harvest-related declines.

Regulations (Texas Turtle Regulations)  implemented by Texas Parks and Wildlife Department (TPWD) in 2007 limited commercial collection of freshwater turtles to four species (common snapping turtle, red-eared slider, smooth softshell and spiny softshell turtles) and prohibited all commercial collection from public waters. Some states (Alabama, Florida) have implemented statewide bans on commercial collection from both public and private waters due to concerns about the long-term conservation of their freshwater turtle species.

TPWD’s regulatory changes led to a decline in the number of turtles harvested, according to annual reports submitted to TPWD by nongame dealers.  A total of 5,430 turtles were reportedly harvested in 2007 (the last year in which widespread commercial collection was legal).  Annual harvest numbers have averaged 495 turtles per year since 2008. Although commercial turtle collection in Texas appears to have waned in recent years, demand for harvested turtles will continue to be influenced by global market demands.

While it appears that commercial take of freshwater turtles in Texas has decreased, it is unclear if this decrease is due to a decline in turtle numbers (and, therefore, availability), under-reporting of harvest, or a lull in commercial activity.  The U.S. Fish and Wildlife Service has announced a proposed rule (FWS-HQ-ES-2013-0052-0001) to address the growing threat of illegal take and trade in native turtles. If finalized, this action will bring three of Texas’ freshwater turtle species, the common snapping turtle, smooth softshell turtle, and spiny softshell turtle, under the protection of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) and require exporters to obtain a permit before shipping turtles overseas.

Evaluation of the current state of freshwater turtle commercial collection in Texas will be a focus of the Nongame and Rare Species Program this year.  If you have any information you would like to share regarding this practice in the state, please email andy.gluesenkamp@tpwd.texas.gov.

One thought on “Freshwater Turtles: Misconceptions and Commercial Collection

  1. Sam January 7, 2015 / 8:31 pm

    Thanks for posting this, Andy.

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