Monitoring Movement Patterns of Juvenile Smalltooth Sawfish (pristis Pectinata) Using Acoustic Monitoring and Tracking in a Nursery Habitat in Southwest Florida PDF Download

Author: Lisa Hollensead
Publisher:
ISBN:
Category : Conservation biology
Languages : en
Pages :

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Book Description
ABSTRACT: Habitat use studies can be used to both investigate ecological and behavioral patterns of animals as well as provide a useful management tool for conservation planners. However, essential habitat can be difficult to determine for highly mobile marine animals, especially when these species are rare or endangered. While critical habitat has been very broadly delineated for the endangered smalltooth sawfish (Pristis pectinata), essential fish habitat (EFH) within the nursery has not been fully described. I used telemetry methods to determine daily activity spaces and rates of movement (ROM) of juvenile P. pectinata in a nursery in southwest Florida. These results were tested for differences in diel and tidal patterns of activity. Seven juvenile animals ranging in size from 85 - 175 cm fork length were tagged in April - September 2011. Overall, activity spaces ranged from 0.07 - 0.17 km2 using 95% Minimum Convex Polygons (MCP), 0.01 - 0.16 km2 based on 50% kernel density estimates (KDE), and 0.08 - 0.68 km2 based on 95% (KDE). Average ROMs ranged from 2.4 - 6.1 meters/min. Activity space and ROMs reflected the morphology of the bay in which the animal was tracked such that fish in small bays had small activity spaces and ROMs. There were no detectable differences in activity space or ROM between ebb and flood tide or high or low tide. Activity space decreased and ROM increased at night indicating possible foraging behavior at night. A home range (1.7 km2) was calculated for one animal. Daily asymptotes in space used were reached for all other tracks suggesting daily activity spaces were determined despite relatively short tracking durations. Bays, estuaries, and other discrete coastal habitats are highly productive and serve as nurseries for a variety of marine fishes. Nurseries are particularly crucial for batoids whose life histories are dependent on rapid growth in the first year, and they may be especially important for rare or endangered species within the group. The smalltooth sawfish, Pristis pectinata, are an endangered marine elasmobranch that makes use of specific nurseries in southwest Florida. While habitat and environmental parameters have been described within the nursery, specific characteristics of the habitats, such as mangrove morphology and sediment types associated with habitat use have not been identified. Two mangrove characteristics (prop root density and limb overhang) and two sediment characteristics (percent organic and percent silt) were used as independent variables to construct a habitat model. Acoustic monitoring was used to examine long term (weeks or months) patterns in habitat use in nursery areas during the critical first year of life. Twenty young-of-the-year sawfish were acoustically tagged between April and October of 2011, and detected by an array of 32 VEMCO VR2w receivers in a documented nursery within Everglades National Park. Presence in the array for individual smalltooth sawfish ranged from one day to 197 days, and overall P. pectinata were present within the acoustic array for 334 days. There was also evidence of overwintering specifically in Chokoloskee Bay. In the back water region (Turner River, Mud Bay, Cross Bays, Wilderness Waterway, and Lopez River), residency times were longer in tidal bays rather than creeks or rivers. A potential emigration corridor from the back water region was observed through the Lopez River. Using receiver data for animals moving between neighboring areas, a step wise logistic regression model in a generalized linear model framework for receiver hits per hour was significant for mangrove prop root density (Stepwise GLM- Partial R square = 0.22, C(p) = 6.02 p = 0.023). This model indicated a higher probability of seeing a juvenile smalltooth sawfish when mangrove prop root density was high.