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Environmental influences on the spatial ecology of juvenile smalltooth sawfish (Pristis pectinata): results from acoustic monitoring.

Simpfendorfer CA, Yeiser BG, Wiley TR, Poulakis GR, Stevens PW, Heupel MR - PLoS ONE (2011)

Bottom Line: The distance between 30-minute centers of activity was typically <0.1 km, suggesting limited movement over short time scales.Salinity electivity analysis demonstrated an affinity for salinities between 18 and at least 24 psu, suggesting movements are likely made in part, to remain within this range.Thus, freshwater flow from Lake Okeechobee (and its effect on salinity) affects the location of individuals within the estuary, although it remains unclear whether or not these movements are threatening recovery.

View Article: PubMed Central - PubMed

Affiliation: Center for Shark Research, Mote Marine Laboratory, Sarasota, Florida, United States of America. colin.simpfendorfer@jcu.edu.au

ABSTRACT
To aid recovery efforts of smalltooth sawfish (Pristis pectinata) populations in U.S. waters a research project was developed to assess how changes in environmental conditions within estuarine areas affected the presence, movements, and activity space of this endangered species. Forty juvenile P. pectinata were fitted with acoustic tags and monitored within the lower 27 km of the Caloosahatchee River estuary, Florida, between 2005 and 2007. Sawfish were monitored within the study site from 1 to 473 days, and the number of consecutive days present ranged from 1 to 125. Residency index values for individuals varied considerably, with annual means highest in 2005 (0.95) and lowest in 2007 (0.73) when several P. pectinata moved upriver beyond detection range during drier conditions. Mean daily activity space was 1.42 km of river distance. The distance between 30-minute centers of activity was typically <0.1 km, suggesting limited movement over short time scales. Salinity electivity analysis demonstrated an affinity for salinities between 18 and at least 24 psu, suggesting movements are likely made in part, to remain within this range. Thus, freshwater flow from Lake Okeechobee (and its effect on salinity) affects the location of individuals within the estuary, although it remains unclear whether or not these movements are threatening recovery.

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Predictions of river distance (contour lines, colors) based on salinity and sawfish length from the best fitting Generalized Additive Model for Pristis pectinata in the Caloosahatchee River.Blues indicate areas downstream of the study area, green indicates low reaches of the study area, yellow mid-reaches and white upper reaches.
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pone-0016918-g008: Predictions of river distance (contour lines, colors) based on salinity and sawfish length from the best fitting Generalized Additive Model for Pristis pectinata in the Caloosahatchee River.Blues indicate areas downstream of the study area, green indicates low reaches of the study area, yellow mid-reaches and white upper reaches.

Mentions: The best fitting GAM model included the factors salinity, length, and the interactions salinity*length, and month*length (Table 1). This model demonstrated that as salinity increased sawfish moved upriver, but that the salinities that different size classes moved at were different (Figure 8). The model predicted that neonate individuals (<100 cm) had limited movements in relation to salinity, while individuals between 100 cm and 140 cm (up to ∼1 year old) moved further upriver and started moving at the lowest salinities. Individuals from 141 cm to 180 cm (1–2 years old) were predicted to move upriver at much higher salinities (i.e., they may be more tolerant of salinity changes), and not move as far as the 100 cm to 140 cm size class. Individuals >180 cm were predicted to have limited movements in relation to salinity, although sample sizes were relatively small. The interaction between month and length probably occurred because of the rapid growth of this species [18] that meant particular size classes were only available in particular months, and so accounting for this through the interaction increased the fit of the model.


Environmental influences on the spatial ecology of juvenile smalltooth sawfish (Pristis pectinata): results from acoustic monitoring.

Simpfendorfer CA, Yeiser BG, Wiley TR, Poulakis GR, Stevens PW, Heupel MR - PLoS ONE (2011)

Predictions of river distance (contour lines, colors) based on salinity and sawfish length from the best fitting Generalized Additive Model for Pristis pectinata in the Caloosahatchee River.Blues indicate areas downstream of the study area, green indicates low reaches of the study area, yellow mid-reaches and white upper reaches.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3037940&req=5

pone-0016918-g008: Predictions of river distance (contour lines, colors) based on salinity and sawfish length from the best fitting Generalized Additive Model for Pristis pectinata in the Caloosahatchee River.Blues indicate areas downstream of the study area, green indicates low reaches of the study area, yellow mid-reaches and white upper reaches.
Mentions: The best fitting GAM model included the factors salinity, length, and the interactions salinity*length, and month*length (Table 1). This model demonstrated that as salinity increased sawfish moved upriver, but that the salinities that different size classes moved at were different (Figure 8). The model predicted that neonate individuals (<100 cm) had limited movements in relation to salinity, while individuals between 100 cm and 140 cm (up to ∼1 year old) moved further upriver and started moving at the lowest salinities. Individuals from 141 cm to 180 cm (1–2 years old) were predicted to move upriver at much higher salinities (i.e., they may be more tolerant of salinity changes), and not move as far as the 100 cm to 140 cm size class. Individuals >180 cm were predicted to have limited movements in relation to salinity, although sample sizes were relatively small. The interaction between month and length probably occurred because of the rapid growth of this species [18] that meant particular size classes were only available in particular months, and so accounting for this through the interaction increased the fit of the model.

Bottom Line: The distance between 30-minute centers of activity was typically <0.1 km, suggesting limited movement over short time scales.Salinity electivity analysis demonstrated an affinity for salinities between 18 and at least 24 psu, suggesting movements are likely made in part, to remain within this range.Thus, freshwater flow from Lake Okeechobee (and its effect on salinity) affects the location of individuals within the estuary, although it remains unclear whether or not these movements are threatening recovery.

View Article: PubMed Central - PubMed

Affiliation: Center for Shark Research, Mote Marine Laboratory, Sarasota, Florida, United States of America. colin.simpfendorfer@jcu.edu.au

ABSTRACT
To aid recovery efforts of smalltooth sawfish (Pristis pectinata) populations in U.S. waters a research project was developed to assess how changes in environmental conditions within estuarine areas affected the presence, movements, and activity space of this endangered species. Forty juvenile P. pectinata were fitted with acoustic tags and monitored within the lower 27 km of the Caloosahatchee River estuary, Florida, between 2005 and 2007. Sawfish were monitored within the study site from 1 to 473 days, and the number of consecutive days present ranged from 1 to 125. Residency index values for individuals varied considerably, with annual means highest in 2005 (0.95) and lowest in 2007 (0.73) when several P. pectinata moved upriver beyond detection range during drier conditions. Mean daily activity space was 1.42 km of river distance. The distance between 30-minute centers of activity was typically <0.1 km, suggesting limited movement over short time scales. Salinity electivity analysis demonstrated an affinity for salinities between 18 and at least 24 psu, suggesting movements are likely made in part, to remain within this range. Thus, freshwater flow from Lake Okeechobee (and its effect on salinity) affects the location of individuals within the estuary, although it remains unclear whether or not these movements are threatening recovery.

Show MeSH
Related in: MedlinePlus