Recent colonization of the headwaters of Fisheating Creek

Recent colonization of the
headwaters of Fisheating Creek
watershed by African Jewelfish
Betsie B. Rothermel and Jason H. O’Connor
Restoration Ecology and Herpetology Program
Introduction
• About 52 species of exotic fish are established in FL
– Nearly half are in Family Cichlidae
– The most species-rich vertebrate family
– Native to Africa and South America
• Traits that predispose cichlids to thrive in novel environments:
– Generalist predators
– Broad physiological tolerances
– Parental care
– Aggressive behavior
– High reproductive potential
Image: http://cichlid.umd.edu/cichlidlabs/kocherlab/bouillabase.html
A highly successful invader –
the African Jewelfish
(Hemichromis letourneuxi)
Native range: north and northwestern part of Africa
Maximum length: 12 cm
Color: males turn deep red in the breeding season
Ecophysiology (experiments by Schofield et al.):
•
High tolerance to low dissolved oxygen (hypoxic conditions)
•
Very tolerant of salinity - 100% survival in 50 ppt (if allowed
to transition gradually from freshwater to marine)
•
Limited by low temperatures – dies at 9-13°C (same is true
for Mayan Cichlid, Cichlasoma urophthalmus)
Introduced range (FL & Puerto Rico)
L. Nico, P. Fuller, P. J. Schofield, and M. Neilson. 2014. Hemichromis letourneuxi.
USGS Nonindigenous Aquatic Species Database, Gainesville, FL.
http://nas.er.usgs.gov/
Case Study: Invasion of an agriculturally modified
landscape in the headwaters of Fisheating Creek watershed
Archbold Reserve
Highlands Co., FL
3,648 acres
Methods
Minnow trapped 45 wetlands on
the Reserve in Sept-Oct 2011
• Trapped until Jewelfish were detected
or until the pond accrued 5 trap-nights
per 1000 m2
• Determined catch-per-unit-effort (CPUE) of fish, larval anurans,
and macroinvertebrates
Gut contents analysis
• Dissected 864 Jewelfish (81% were adults ≥ 4.7 cm) and
attempted to identify prey items in individuals > 5 g
Predation trial in the lab
• Do Jewelfish attack and consume tadpoles at the same rate as a
native fish predator (Warmouth)?
Distribution of African
Jewelfish:
• 22% of ponds in 2011
• Mostly restricted to ponds
connected by ditches or in
close proximity to Mary’s
Creek and Frances Creek
• Brown Hoplo
(Hoplosternum littorale)
have a wider distribution
Photo: H. Jelk
http://nas.er.usgs.gov/
Relative abundance (CPUE)
10
Captures per Trap*night
9
8
7
6
5
4
3
2
1
0
Factors influencing exotic fish distribution/abundance
Significant factors:
Predicted Probability of Occurrence
1.0
0.9
• Probability of Jewelfish
occurrence increased with
wetland area
0.8
0.7
0.6
0.5
0.4
0.3
Jewelfish Absent
0.2
Jewelfish Present
0.1
Predicted
• CPUE of both native and
exotic fish increased as
distance to nearest
ditch decreased
0.0
0
5
10
15
Wetland Area (1,000 m2)
20
25
Colonization of Fisheating Creek watershed
1st detected on
Archbold Reserve
2008
Established in
Reserve wetlands
2011
Lower Fisheating Creek
(Palmdale) 2004
Upper Caloosahatchee
River 2004
Gut Contents
0.6
Proportion of Stomachs
0.5
0.4
0.3
0.2
0.1
0
Fish
Arthropod
Prey Type
Plant
Nothing
Identifiable
African Populations
Floridian Populations
Arthropods
Fish
Plant Material
Arthropods
Fish
Plant Material
• Our results likely biased
– Fish predation may be overestimated
– Tadpole predation probably underestimated
• These biases likely confound diet analyses in other
studies
– The reason tadpoles have not been reported as prey?
Predation trial
• Presented 1 Jewelfish or 1 Warmouth (Lepomis
gulosus) predator (n = 10 of each predator species)
with 1 Green Treefrog (Hyla cinerea) tadpole
• Observed for first 10 min and hourly thereafter
• Recorded time to attack and fate of prey (alive, dead,
fully consumed, or partially consumed)
• Trial lasted 16 hrs
Results:
12
70%
partially
consumed
20% fully
consumed
Number of Tadpoles
10
Half the Jewelfish
attacked the
tadpole within the
first 2 hrs
8
6
(Warmouth took
much longer)
4
2
0
Hemichromis
Lepomis
Potential impacts of African
Jewelfish:
• Capture rates for 16 of 25 native taxa
(including all frogs) were lower in
wetlands with Jewelfish
• However, we did not find significant
effect on species richness
• Exotic fish abundance was positively
correlated with abundances of:
- Eastern Mosquitofish (Gambusia holbrooki)
- native topminnows (Fundulus spp.)
- Giant Diving Beetle (Cybister fimbriolatus)
Mesocosm experiment
Schofield et al. (2014) Hydrobiologia 722:171-182
Predator:
Small native fish:
Invertebrates:
Submerged aquatic
vegetation:
Dollar Sunfish (Lepomis)
Eastern
Mosquitofish
(Gambusia)
Flagfish
(Jordanella)
Least Killifish
(Heterandria)
Grass shrimp
(Palaemonetes)
Snails
(Planorbella,
Physella)
Florida Applesnail
(Pomacea)
X
Hydrilla
After 8 months:
- Significantly reduced biomass of Planorbella snails (vs. controls)
- Little/no reproduction by Jordanella (also true in tanks with Jewelfish)
- Final mean density of small native fish = 15/m2 (vs. 19/m2 in control)
Schofield et al. (2014) Hydrobiologia 722:171-182
Predator:
Small native fish:
Invertebrates:
Submerged aquatic
vegetation:
African Jewelfish (Hemichromis)
Eastern
Mosquitofish
(Gambusia)
X
Flagfish
(Jordanella)
X
Snails
(Planorbella,
Physella)
Grass shrimp
(Palaemonetes)
X
X
Least Killifish
(Heterandria)
Florida Applesnail
(Pomacea)
Hydrilla
- Grass shrimp and snails nearly eliminated
- Significantly reduced biomass of Heterandria (vs. controls or Lepomis)
- Lower biomass of Gambusia (though not statistically significant)
- Final mean density of small native fish = 6/m2
Porter-Whitaker et al. (2012) Ecology of Freshwater Fish 21:375-385
4-day trials in 1-m2 field enclosures:
- No significant effects on grass shrimp, Heterandria, or Gambusia
- Significantly higher mortality of Jordanella in cages with Jewelfish
- Jordanella used in this experiment were much smaller (easier prey?)
- Overall, Mayan cichlids had stronger effects on native prey species than
Jewelfish
-
but this might have been because Jewelfish spent more time fighting
with each other and less time feeding…!
Conclusions
• In invaded wetlands, the African Jewelfish is now one of the most
common fish species
• Despite similar size and trophic position as some native fish
(Lepomis) they are not functionally equivalent predators:
- reduce species at the base of the food web
- mechanisms (direct vs. indirect interactions)
still unclear
- threat to small native fish because of their
aggressive behavior and ability to use more
temporary aquatic refuges
Conclusions (cont.)
• Larger (and deeper) ponds may facilitate spread/establishment
in agricultural landscapes:
- More ditch connections
- Greater habitat heterogeneity and abundances of prey
- Deeper water serves as refuge from cold
• No known control options
- Preventing introduction is key
- Another consideration for
wetlands restoration efforts
Acknowledgments
• GIS assistance - Roberta Pickert (Archbold GIS lab)
• Field assistance – Josh Daskin, Justin Dee, Zachery
Forsburg, Heidi Henrichs, David Moldoff