Do Marine Reserves in Florida Keys National Marine Sanctuary Protect Spiny
Lobsters?
Carrollyn Cox
Florida Fish and Wildlife Conservation Commission, Florida Marine Research
Institute, Marathon, FL
If marine reserves in the Florida Keys National Marine Sanctuary are effective in
protecting spiny lobsters, Panulirus argus, from harvest, we expect that lobsters
will become larger and more abundant inside the reserves compared to exploited
areas. To determine reserve effectiveness, we monitored spiny lobsters in thirteen
pairs of reserves and exploited reference areas twice a year from 1997-2001.
Samples were taken during July (the end of the closed fishing season) and during
September/October after several months of the fishing season. Reserves were
comprised of 11 ( = 82 ha) Sanctuary Preservation Areas and Research Reserves
(SPAs), one large (515 ha) SuperSPA, and one 3,000 ha Ecological Reserve (ER).
Sampling was stratified by habitat type (forereef, backreef, offshore patch reef,
nearshore patch reef) in the ER and three subsamples were taken on each habitat;
three subsamples were taken on the forereef at the SuperSPA, and one sample was
taken at the other eleven SPAs. Sampling consisted of a 60-minute search during
which we counted and attempted to catch and measure all lobsters observed. Data
from SPAs, the SuperSPA, and the ER were analyzed separately and compared
with data from their respective exploited reference areas. Additionally, Looe Key
SPA and its reference area were treated separately because Looe Key has been a
marine reserve since 1981.
In 1997, mean lobster size was below
1. Size of lobsters in Florida Keys National
the legal limit in both reserves
Marine Sanctuary, 1997-2001.
(excluding Looe Key) and
Ecological Reserve
SuperSPA
references. Since protection, mean
lobster size in reserves has
generally been larger than legal
size, whereas it remained at or
below the legal limit in exploited
areas (Fig. 1). In all years, mean
SPAs
Looe Key
size of legal lobsters was larger in
reserves than in references.
Additionally, abundance of very
large lobsters (> 100 mm CL)
increased in the ER relative to its
reserve
reference
reference area.
90
85
Mean Size (mm CL + 1 SE)
80
75
70
65
60
1997
1998
1999
2000
2001
1997
1998
1999
2000
2001
1997
1998
1999
2000
2001
90
85
80
75
70
65
60
1997
1998
1999
2000
2001
Lobster abundance varied among years with a high in1999 and a low in 1998.
Lobsters were much more abundant in Western Sambo ER and its reference than
elsewhere. There were always fewer lobsters in Carysfort SuperSPA than in its
reference. In most years, abundance declined in both reserves and references
during the open season, but the decline was less precipitous in reserves (Fig. 2).
The decline in lobster abundance inside reserves during the fishing season
indicates that overall, the reserves are too small to totally protect lobsters from
harvest. However, viewed separately, several of the reserves, including the ER,
appear to provide at least a temporary refuge for spiny lobsters, while others do
not appear to function as lobster reserves at all. Effectiveness appears to be a
function of reserve size, location, and habitat protected.
Total Number of Lobsters Observed
2. Total number of lobsters observed in FKNMS reserves and reference
areas during closed (c) and open (o) fishing seasons, 1997-2001.
1000
800
600
400
200
reserve
reference
0
c
o
1997
c
o
1998
c
o
1999
c
o
2000
c
o
2001
In 2002, we focused on the Western Sambo ER, because it has shown signs of
effectiveness. We discontinued sampling at all other reserves except Looe Key
SPA because it has been a lobster reserve for more than 20 years, and Eastern
Sambo Research Reserve because it is close to the ER and lobsters have been very
abundant there. A relative abundance index (RAI) of legal-sized lobsters during
the closed season was calculated to account for natural yearly variation in lobster
abundance. RAI was calculated as the mean abundance of legal lobsters in the
reserve minus mean abundance legal lobsters in the corresponding exploited area
each year (Fig. 3).
3. Relative abundance index of legal-sized lobsters on
forereef habitat during the closed fishing season, 1997-2002.
Western Sambo Ecological Reserve
50
Relative Abundance Index (RAI)
40
30
20
10
0
-10
-20
-30
-40
1997
1998
1999
2000
2001
2002
Eastern Sambo Research Reserve
Looe Key SPA
50
40
30
20
10
0
-10
RAI
-20
-30
-40
1997
1998
1999
2000
2001
2002
1997
1998
1999
2000
2001
2002
Abundance of legal-sized lobsters on the forereef at Western Sambo ER during
the closed fishing season relative to that in the exploited area has been increasing
each year since the reserve was created. The same cannot be said of lobster
abundance at Looe Key SPA. The probability of a lobster wandering outside of a
small protected area during its daily life is high. Additionally, the smaller
protected areas encompass only a single habitat type. Our data indicate that a
residential population of spiny lobsters is becoming established within Western
Sambo Ecological Reserve. The expansion of lobster size-frequency in the ER
suggests that some of the lobsters remain in the reserve for an extended period of
time. Habitat for all lifestages of spiny lobsters is protected within the reserve.
Once adults establish residence, the ecological reserve is sufficiently large to
protect a portion of the population as they travel to foraging grounds and between
winter dens and spring spawning habitat.
Carrollyn Cox, Florida Fish and Wildlife Conservation Commission, Florida
Marine Research Institute, Marathon, FL, 33050, Phone: 305-289-2330, Fax: 305289-2334, carrollyn.cox@fwc.state.fl.us, Other coastal ecosystems