Annual Update Duval County Manatee Protection Plan Population Inventory and Analysis

Transcription

1 Annual Update Duval County Manatee Protection Plan Population Inventory and Analysis Prepared by Jacksonville University for the Waterways Commission of the Jacksonville City Council. September

2 THIS REPORT CONTAINS THE FOLLOWING UPDATED SECTIONS TO THE 1999 DUVAL COUNTY MANATEE PROTECTION PLAN: 1. INTRODUCTION, INVENTORY ANALYSIS SECTION (PAGES 3-7). 2. TABLES SECTION (PAGES 8-14). 3. FIGURES SECTION (PAGES 15-23). 4. SERIES A AERIAL SIGHTINGS (PAGES 24-30). 5. SERIES B MANATEE MORTALITY 2001 (PAGE 31). 2

3 Introduction The Duval County Manatee Protection Plan (MPP) was developed by the Jacksonville Waterways Commission for the Jacksonville City Council. Jacksonville University conducted the research on which the plan is based. Extensive studies were conducted beginning in 1994 and have continued to present. In 1999, the State of Florida approved the Duval County Manatee Protection Plan. The Plan had initially been approved by the Florida Department of Environmental Protection. In April 2000, the state rule implementing the boat speed zones were adopted by the Florida Fish and Wildlife Conservation Commission. The MPP contains a provision that the plan be reviewed and updated annually. This report contains additional data concerning the manatee population in Duval County and is the 2001 annual update. Updated information is shown in bold. Inventory and Analysis Manatees Distribution and Abundance: Aerial surveys by Jacksonville University (March, September, 2001) conform to current FDEP Manatee Aerial Survey Protocol. Intensive bimonthly surveys were conducted in areas manatees frequent - the St. Johns River, its tributaries and the Atlantic Intracoastal Waterway (Nassau Sound to Palm Valley). During winter months, industrial warm water sources in Northeast Florida are also monitored. During 315 bimonthly surveys, a total 6,661 manatees have been observed, 8.2 calves (Table 1). When water temperatures decrease (December through March), the majority of manatees in Duval County waters migrate south to Blue Springs and/or other warmer South Florida waters. Historical manatee survey data from Jacksonville University indicate that manatees were observed feeding, resting and cavorting/mating in greater numbers south of the Fuller Warren Bridge relative to other waters in Duval County. Sightings in remaining waters consisted mostly of manatees traveling or resting. Preliminary data suggested that manatees use the Intracoastal Waterway as a travel corridor during their seasonal (north/south) migrations along the east coast. Data indicated that manatees stay close to the shore, utilizing small tributaries for feeding when in these waters. Aerial survey counts of manatees are indices of abundance at the time of each survey. As a result, counts must be viewed as relative only to trends in general abundance, distribution countywide, and habitat use patterns (Irvine 1980). Map Series A, Manatee Aerial Sightings, provides graphical distribution information about manatees. Differences in seasonal distribution patterns for manatees in was not found to be significantly different from past years ( ). Map Series A, shows manatee distribution from Summer 2000 through Summer Seasons were classified as Winter (December- February), Spring (March-May), Summer (June-August), and Fall (September-November). 3

4 The proportion that calves represented of the total number of manatees sighted ranged from 3.97 to (LSJR) and 2.3 to (ICW) over the duration of the study (Table 1). These proportions were similar to those reported by Campbell and Irvine (1978) of 9.6, Valade (1991) 5 and Kinnaird (1983) 7 for LSJR, Duval County. Percentages for the 2000 season were lower in the ICW (4) but not significantly different for the same months in 2001, possibly attributed to unusual weather conditions in the past couple of years. Mean Single Highest Day Counts (SHDC) for LSJR was 106 manatees per survey between SHDC for the 2000 and 2001 was considerable lower than previous years (67 and 85 manatees per survey respectively). Dry weather caused higher salinity in the LSJR which lead to poor or no regeneration of tape grass beds which manatees primarily rely on for food. As a result, over all per survey counts were generally lower than expected. A part from the year 2000 data, it appears that highest day counts have increased but they are not statistically different from the 99 manatees per survey reported by Valade (1991). Increased counts may be attributed to observers having gained a better knowledge of the survey area and where manatees are likely to occur. In the ICW the mean SHDC was 18 manatees per survey. SHDC of 23 manatees in 2001 was higher than 13 manatees in the 2000 and 12 reported in The 2001 count appears to be more consistent with counts prior to the period of drought for years (Table 1). Cumulative counts of manatees at various locations in the ICW (Table 2) and LSJR (Table 3) are included to show density abundance and location of manatees in the County. The latter does not appear to have changed in spite of the lower numbers of manatee observed during the season. Increased spring and summer sightings are attributed to an influx of animals from outside the study area (Figure 1-2). Some of these animals came from Blue Springs (170 Km further south within the St. Johns River system) and the rest are made up of south Florida east coast animals (Kinnaird 1983). Kinnaird (1983) mentioned the then current population of Blue Springs animals numbering some 35 in 1982/83. Ackerman (1995) mentions 88 identified manatees at Blue Springs in the winter of Counts at Blue Springs were 114 manatees ( ), 132 ( ) and 120 ( ) (Hartley personal communication). Satellite telemetry data support that most animals come into the LSJR as a result of south Florida east coast animals migrating north/south each year (Ackerman personal communication.). Sightings by Jacksonville University seem to indicate that the majority of animals moving into the County come from further south within the LSJR system (Map Series A). However, scar pattern identification suggests that significant numbers of manatees are part of the Atlantic sub-population and that in the last decade, only one manatee has been identified as coming from the Blue Spring population that has been recovered dead in Duval County (Beck personal communication). Manatees were distributed throughout LSJR and ICW waters in spring (Map Series A). Highest concentrations of manatees occurred south of Fuller Warren Bridge (east and west banks) and Doctor s Lake in summer where substantial submerged aquatic vegetation exists. 4

5 In 2001 manatees seemed to be more spread out throughout the county than in 2000 and this may be due to the fact than manatee were forced to spend more time traveling in search of sparse food resources. In late summer and fall manatees tended to occur in the main stem of LSJR. This was perhaps because tributary waters became too warm and uncomfortable for, most animals moved south out of Duval County. During spring and summer, manatees with new calves were consistently seen in the back waters of tributaries because these areas are more sheltered. Wills Branch Creek continues to be one such birthing area in Cedar River. Manatees spent most of the time resting, followed by traveling and feeding and least time was spent cavorting. In winter it was difficult to find manatees feeding because manatee abundance was low. Also, no manatees were observed cavorting in winter. Winter variances for resting and traveling animals was larger because of fewer sightings and resting animals congregated at power plants. Spring and summer of data appear to be similar in that the percent of manatees observed traveling was higher in the past two years than before (98-99) and percent resting was lower than before. The apparent change in behavior may be because of dry weather conditions, higher than normal salinity and the resulting low food availability which may have caused the manatees to travel more in search of food than previous years. Indices for feeding remain unchanged for the most part although percent cavorting seems to have increased in summer 2001 (Table 4). Tape grass grows well from 0-12 ppt and can tolerate waters with salinities up to ppt for short periods of time. Growth becomes limited above about ppt based on analyses of high-estuarine distribution (Twilly and Barko ). The availability of tape grass decreased significantly in the County during the past two years because low precipitation caused higher than usual salinity values (Figure 3). The pattern of mean numbers of manatees observed seasonally in the LSJR and the ICW seem to be consistent with those observed in previous years (Figure 4-5). Behavior patterns in the ICW remain predominantly unchanged from those observed between Generally lower numbers of manatees were observed in the 2000 season. Feeding percentages are consistent with the last few years. In previous years no cavorting behavior was observed however, in the springs of both 1999 and 2000 manatees were observed cavorting in the ICW. No manatees were seen cavorting in the ICW in Mortality Information: The total of State-wide deaths documented for 2000 was 273, of which 78 were watercraft-related. Other causes included other human (8), perinatal (58), cold stress (14), other natural (37), flood gate (8) and undetermined (62). Watercraft deaths for the key counties totaled 58. Other causes of death for the key counties included other human (5), perinatal (47), cold stress (9), other natural (29), flood gate (4) and undetermined (50) (Figure 6). Watercraft caused mortality of manatees in Florida compared for the years 1998 to September, 2001 is illustrated in Figure 7. Watercraft, perinatal and undetermined causes of death were the most 5

6 significant for Total mortality rates for manatees in Duval County decreased from 19 deaths per year in 1991 to 9 deaths per year in 1999 and was 11 in 2000 (Table 6, and Figure 8). As of September 2001 there were a total of 5 reported deaths in Duval County of which, 2 were undetermined, 2 were cold stress and 1 perinatal (Thomas Pitchford personal communication.) Table 7. shows manatee mortality caused by watercraft-related impacts and serves as a comparison of Duval County to other counties in Florida from 1990 through Mortality due to watercraft impacts in 2000 was highest in Brevard and Lee Counties (13). Intermediate numbers of watercraft-caused deaths were documented in Collier (5) Duval and Indian River (4) Sarasota (5) and Volusia (4); and lower numbers of deaths were documented in the remaining relevant counties, including Broward (1) Citrus (1) Dade (2) Martin (1) Palm Beach (3) and St. Lucie (1). Watercraft-caused mortality in Duval County has remained low at 2 to 3 deaths per year between It was 4 deaths per year in 2000 (Table 7) and 0 as of September Table 8. shows total manatee mortality/yr. by cause in Duval County from 1976 to the end of July Map Series B, Duval County Manatee Mortality 2001 shows locations of carcass recoveries. The maps for 2000 have not been made available yet on CD-ROM so no changes were included in this update. Warm-Water Attractants: In Duval County warm water discharges consist of three power generating stations and two paper mills (Map Series A). Area power plants include: St. Johns River Power Park and Southside and J.D. Kennedy Generating Stations. Seminole Kraft and Jefferson Smurfit Containerboard Corporation are the two paper mills in Duval County. Each of these areas provides warm-water refuges for manatees in the winter months and during periods of cold weather. At the present time, Southside and J. D. Kennedy Generating Stations are routinely monitored by JU when they are operating during cold weather. Data recorded encompasses: number of manatees, percentage of adults to calves, scar patterns (sketched for identification), water temperature at the outfall, and river-water temperature. Information in the form of photographs and video footage is also collected. The latter information will help to document the nature of Florida manatee usage and activities at generating stations in Jacksonville. In addition, there has been a significant reduction in other power plant operations since St. Johns River Power Park came on line. Consequently, manatee movement patterns in Duval County for the next several years are likely to be affected. Thus, it will be necessary for warm-water discharges in Duval County to be monitored on a continual basis. During winter, manatees remaining in the area assembled in groups at warm water out falls. Jacksonville Electric Authority s Southside (JEASS) and Kennedy Generating Stations (JEAKS) and Jefferson Smurfit s paper mill are located within a 7 mile radius of Downtown. In 1998, JEASS and JEAKS sites were monitored daily between 11/1 to 12/3. Total daily count varied from 0-6 animals (3 adults were observed on 11/6, 1 adult and calf on 11/9, and 4 adults and 2 calves on 11/13). No manatees were observed at JEAKS. 6

7 In 1999, the same sites were monitored between 11/11/99 to 2/3/2000. Total daily count at JEASS varied from 0-16 between 11/11/99 to about 12/25/99. No manatees were observed between 12/26/99 to 1/24/2000, then 1 adult was observed on 1/25/2000. Total daily count varied from 0-16 at JEAKS and manatees were generally observed between 11/10/99 to 12/12/99. No manatees were seen between 12/12/99 to 1/25/2000, then a single adult was recorded 1/26/2000. In 2000, the same sites were monitored between 11/03/00 to 3/31/2001. Total daily count at JEASS varied from 0-29 between 11/03/00 to about 1/24/01. This represents the highest count at JEASS since monitoring began in Relatively lower numbers of manatees were observed between January to March Four manatees were rescued by Sea World of Florida, 3 manatees about 1/3/01 and 1 manatee on 1/24/01. JEAK was not operational and occasional animals observed seemed to be just passing through on their way to JEASS (Figure 9). 7

8 TABLE 1. Summary of the total number of aerial surveys, adults and calves observed, and Single Highest Day Counts (SHDC) by year. Year No. of Adults Calves Total Calves SHDC surveys LSJR Total ICW Total SHDC=Single Highest Day Count 1 March to the end of December 2 January to September 3 Mean Calves 4 Mean highest day count 8

9 TABLE 2. Total aerial sightings of manatees in the Intercoastal Waterway, Duval Co., FL. (March 1994-September 2001). LOCATION ADULTS* CALVES* TOTAL* Nassau Sound Sawpit Creek ICW North of Fort George River Sisters Creek Fort George Inlet Mayport St. Johns Bluff Blount Island Mill Cove Atlantic Blvd. Bridge to SJR confluence Beach Blvd. Bridge to Atlantic Blvd JTB Bridge to Beach Blvd. Bridge Palm Valley Bridge to JTB Bridge Container Corporation, Fernandina *These numbers indicate total per survey counts of manatees. Individual manatees may migrate to other areas between flights. Source Jacksonville University Note:No manatees were seen at Container Corp. of America in 1998, 1999 or 2000 since the introduction of a diffuser array on the effluent warm water discharge. 9

10 TABLE 3. Total aerial sightings of manatees in Lower St. Johns River, Duval Co., FL. (March 1994-September 2001). LOCATION ADULTS* CALVES* TOTAL* Quarantine Island Dames Point Trout River Arlington River Pottsburg Creek Miller Creek Downtown San Marco Ortega River Sadler Point Pirates Cove NAS/JAX Mulberry Cove Rudder Club Club Continental Doctors Lake SJR south of Dr.Lake Julington Creek Durbin Creek Mandarin Point Plummers Point Beauclerc Bluff Goodbys Creek Christopher Point Point La Vista Lions Club Boat Ramp JEA - Southside Jefferson Smurfit * These numbers indicate total per survey counts of manatees. Individual manatees may migrate to other areas between flights. Source Jacksonville University

11 Table 4. Number percent of manatees engaged in various activities between spring 1999-summer 2000 (LSJR). Year/Season Total Percentage No. T R F C Winter Spring Summer Fall Winter Spring Summer Fall Winter Spring Summer T=Traveling; R=Resting; F=Feeding and C=Cavorting Source Jacksonville University Table 5. Number percent of manatees engaged in various activities between spring 1999-summer 2000 (ICW). Year/Season Total Percentage No. T R F C Winter Spring Summer Fall Winter Spring Summer Fall Winter Spring Summer T=Traveling; R=Resting; F=Feeding and C=Cavorting Source Jacksonville University

12 TABLE 6. Florida manatee mortality, County # Total Brevard Broward Citrus Collier Dade Duval Indian R no info Lee Martin Palm Bch Sarasota St. Lucie Volusia Total Source FWCC/FMRI of Total 12

13 TABLE 7. Watercraft caused mortality in Florida's Key Counties, County # Total of Total Brevard Broward Citrus Collier Dade Duval Indian R no info Lee Martin Palm Bch Sarasota St. Lucie Volusia Total Source FWCC/FMRI

14 TABLE 8. Causes of manatee mortality in Duval County, Florida July Year Watercraft Human Perinatal Other Natural Undetermined Total/Year * Total Source FWCC/FMRI * = Until September

15 CALVES TOTAL W_TEMP Jan 12-Feb 12-Mar 12-Apr 12-May 12-Jun 12-Jul 12-Aug 12-Sep 12-Oct 12-Nov 12-Dec 12-Jan 12-Feb 12-Mar 12-Apr 12-May 12-Jun 12-Jul 12-Aug Number of manatees Water temperature ( C) 5 0 F Date F FIGURE 1. Aerial sightings of manatees and water temperature in the Saint Johns River 2000 September

16 CALVES TOTAL W_TEMP Jan 12-Feb 12-Mar 12-Apr 12-May 12-Jun 12-Jul 12-Aug 12-Sep 12-Oct 12-Nov 12-Dec 12-Jan 12-Feb 12-Mar 12-Apr 12-May 12-Jun 12-Jul 12-Aug Number of manatees Water temperature ( C) 5 0 Date FIGURE 2. Aerial sightings of manatees and water temperature in the Intracoastal Waterway 2000 September

17 Salinity (ppt) Months FIGURE 3. Mean monthly salinity recorded at the Jacksonville University dock, Duval Co., FL August

18 LN Total (COUNT + 1) SP98 SU98 FA98 WI98 SP99 SU99 FA99 WI99 SP00 SU00 FA00 WI00 SP01 SU01 Season/Year FIGURE 4. Mean counts of manatees in the LSJR by season and year (horizontal lines) between spring 1998 and spring Vertical lines show maximum and minimum counts. Boxes show 5 and 95 confidence intervals of the mean. Summers are shaded black; Winters are shaded gray; Springs and Falls are not shaded. 18

19 LN Total (COUNT + 1) SP98 SU98 FA98 WI98 SP99 SU99 FA99 WI99 SP00 SU00 FA00 WI00 SP01 SU01 Season/Year FIGURE 5. Mean counts of manatees in the ICW by season and year (horizontal lines) between spring 1998 and spring Vertical lines show maximum and minimum counts. Boxes show 5 and 95 confidence intervals of the mean. Summers are shaded black; Winters are shaded gray; Springs and Falls are not shaded. 19

20 60 50 Number of manatee deaths Other Natural Undetermined Perinatal Human Brevard Broward Citrus Collier Dade Duval Flood Gate Watercraft Indian River Lee Martin Palm Beach Sarasota St.Lucie Volusia FIGURE 6. Causes of manatee mortality for Florida s Key Counties,

21 ave Number of manatees Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month FIGURE 7. Watercraft caused mortality of manatees in Florida compared for the years 1998 July (The declining trend line is also a running average for the years ). 21

22 Watercraft Other Human Perinatal Other Natural Undetermined Number of manatee deaths Undetermined Other Natural * Perinatal Other Human Watercraft Year * = September 2001 FIGURE 8. Causes of mortality for manatees in Duval County, Florida ( September 2001). 22

23 Number of manatees / 12/3 01/03 2/12 3/12 3/31/01 13/ /3/ KENNEDY SOUTHSIDE WTemp ( C) Southside WTemp ( C) Kennedy / / Days / / Water temperature ( C) 3/31/01 FIGURE 9. Manatees recorded using daily ground surveys at Southside and Kennedy generating stations in downtown Jacksonville, Duval Co., FL. 23

24 Aerial sightings of manatees 1. The following maps show manatee distribution from Summer 2000 Summer Seasons were classified as follows: Winter - December - February Spring - March - May Summer - June - August Fall - September - November SERIES A - MANATEE AERIAL SIGHTINGS 24

25 SERIES A Manatee aerial sightings, Duval Co., FL (Summer, 2000). NASSAU CO. N ATLANTIC OCEAN Fuller Warren Bridge JEAKS JEASS DUVAL CO. CLAY CO. Buckman Bridge DUVAL CO. ST. JOHNS CO. Source Jacksonville University Note: Each dot represents the location of a sighting, not the number of manatees sighted. 26

26 SERIES A Manatee aerial sightings, Duval Co., FL (Fall, 2000). NASSAU CO. N ATLANTIC OCEAN Fuller Warren Bridge JEAKS JEASS DUVAL CO. CLAY CO. Buckman Bridge DUVAL CO. ST. JOHNS CO. Source Jacksonville University Note: Each dot represents the location of a sighting, not the number of manatees sighted. 27

27 SERIES A Manatee aerial sightings, Duval Co., FL (Winter, ). NASSAU CO. N Fuller Warren Bridge JEAKS ATLANTIC OCEAN JEASS DUVAL CO. CLAY CO. Buckman Bridge DUVAL CO. ST. JOHNS CO. Source Jacksonville University Note: Each dot represents the location of a sighting, not the number of manatees sighted. 28

28 SERIES A Manatee aerial sightings, Duval Co., FL (Spring, 2001). NASSAU CO. N Fuller Warren Bridge JEAKS ATLANTIC OCEAN JEASS DUVAL CO. CLAY CO. Buckman Bridge DUVAL CO. ST. JOHNS CO. Source Jacksonville University Note: Each dot represents the location of a sighting, not the number of manatees sighted. 29

29 SERIES A Manatee aerial sightings, Duval Co., FL (Summer, 2001). NASSAU CO. N Fuller Warren Bridge JEAKS ATLANTIC OCEAN JEASS DUVAL CO. CLAY CO. Buckman Bridge DUVAL CO. ST. JOHNS CO. Source Jacksonville University Note: Each dot represents the location of a sighting, not the number of manatees sighted. 30

30 SERIES B Manatee mortality 2001, Duval Co., FL. NASSAU CO. N Fuller Warren Bridge JEAKS Watercratf 6/19/01 ATLANTIC OCEAN JEASS Cold stress 2/24/01 Buckman Bridge Cold stress 1/21/01 DUVAL CO. CLAY CO. Cold stress 2/17/01 DUVAL CO. Undetermined 4/8/01 ST. JOHNS CO. Source FWCC personal communication 31