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A Review and Updated Assessment ofFlorida's Anadromous Shads: AmericanShad and Hickory ShadRichard S. McBride a & Jay C. Holder ba Florida Fish and Wildlife Conservation Commission , 100 EighthAvenue SE, St. Petersburg, Florida, 33701-5020, USAb Florida Fish and Wildlife Conservation Commission , 5450 U.S.Highway 17, DeLeon Springs, Florida, 32130, USAPublished online: 08 Jan 2011.
To cite this article: Richard S. McBride & Jay C. Holder (2008) A Review and Updated Assessment ofFlorida's Anadromous Shads: American Shad and Hickory Shad, North American Journal of FisheriesManagement, 28:6, 1668-1686, DOI: 10.1577/M07-066.1
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A Review and Updated Assessment of Florida’s AnadromousShads: American Shad and Hickory Shad
RICHARD S. MCBRIDE*1
Florida Fish and Wildlife Conservation Commission,100 Eighth Avenue SE, St. Petersburg, Florida 33701-5020, USA
JAY C. HOLDER
Florida Fish and Wildlife Conservation Commission,5450 U.S. Highway 17, DeLeon Springs, Florida 32130, USA
Abstract.—This paper reviews the history of fishing, regulations, and stock assessments for Florida’s
anadromous shad species—American shad Alosa sapidissima and hickory shad A. mediocris—and assesses
their status in Florida’s St. Johns River based on a creel survey and an electrofishing survey. Historically,
these anadromous shads constituted an important fishery in Florida. Landings were first reported in the 1860s,
and scientific assessments occurred in the 1950s, 1960s, and early 1970s. Netting restrictions effectively
ended the commercial fishery in the 1990s. We used recreational catch rates as a proxy for stock size and
found it to be low but stable during 1993–2005. The mean length of American shad was significantly less
during 2002–2005 than it was historically (1958), and the recent proportions of female American and hickory
shad were significantly lower than the historical proportions. These data were interpreted as demonstrating a
negative, but perhaps only an historical, effect of fishing. The rebuilding of Florida’s anadromous shad stocks
via fishing regulations was not evident; this may require more time, or perhaps factors other than fishing are
interfering with the rebuilding process.
American shad Alosa sapidissima and hickory shad
A. mediocris are anadromous clupeids that spawn in
rivers but spend most of their adult lives at sea. Along
the U.S. East Coast, American shad spawn from
Canada to Florida (Limburg et al. 2003) and hickory
shad from Maryland to Florida (Harris et al. 2007). In
Florida, American and hickory shad spawn during
winter in rivers of the northeastern part of the state;
their juveniles migrate to the lower reaches of the river
and out into coastal habitats during the following fall
(McBride 2000; Trippel et al. 2007).
Worldwide, the biology and management of Alosa
and other shad species (Alosinae) have received
considerable attention (e.g., Limburg and Waldman
2003). In North America, American and hickory shad
constituted very important fisheries, but declining
landings coupled with the expansion of other fisheries
have reduced their economic and cultural importance
(Walburg and Nichols 1967). Along the U.S. East
Coast, anadromous shad stocks are managed by a
fishery management plan (FMP) overseen by the
Atlantic States Marine Fisheries Commission (ASMFC
1985, 1999). In the most recent stock assessment
(ASMFC 2007), over one-half (19 of 32) of the
American shad stocks were reported to be either
declining or unknown; only two stocks were consid-
ered to be increasing in abundance.
This paper presents a case study of American and
hickory shad in Florida’s St. Johns River as an example
of this ongoing stock assessment process by the
ASMFC and its member states. The central east coast
of Florida is the southern limit of the distribution for
both species, and the St. Johns River (Figure 1) is the
only river within Florida with sufficient data for the
analysis of either species (Rulifson 1994; Florida Fish
and Wildlife Conservation Commission, unpublished
data). The St. Johns River is 499 km in length and
flows slowly from south to north; because it drops only
9.1 m in elevation (,2 cm/km) and widens at various
points to create several shallow lakes and appends to
others, it is known as a ‘‘river of lakes.’’
This paper begins with a brief review of the
fisheries, fishing regulations, and stock assessments
of Florida’s American and hickory shad (see McBride
2000 for a more detailed review). The remainder of the
paper assesses the status of these two stocks using data
from recent fishery-dependent and fishery-independent
collections in the upper St. Johns River and, where
appropriate, unpublished data from earlier research by
Florida’s state research programs (e.g., Williams and
Bruger 1972; Williams et al. 1975). The underlying
* Corresponding author: [email protected] Present address: National Marine Fisheries Service,
Northeast Fisheries Science Center, 166 Water Street, WoodsHole, Massachusetts 02543-1026, USA.
Received April 10, 2007; accepted April 21, 2008Published online November 20, 2008
1668
North American Journal of Fisheries Management 28:1668–1686, 2008� Copyright by the American Fisheries Society 2008DOI: 10.1577/M07-066.1
[Article]
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FIGURE 1.—Map of the St. Johns River and related lakes. River lengths are indicated at 100-km intervals from the mouth of the
river near Mayport.
ANADROMOUS SHADS OF FLORIDA 1669
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purposes of this study were (1) to review the available
data and information regarding Florida’s American and
hickory shad and (2) to assess the recovery of these
stocks in light of the extensive reductions in commer-
cial fishing effort that have occurred recently.
Historical Review
Fisheries. —Florida’s native Americans most likely
fished for anadromous fishes, but unlike in other states,
there are no specific records of this (McBride et al.
2003, poster at the 23rd Annual Meeting of the Florida
Chapter of the American Fisheries Society). Commer-
cial shad fishing began in Florida’s St. Johns River as
early as the 1860s (Baird 1874; Osborn 1882; Dempsey
1887), but Florida’s was the last shad fishery to
develop along the U.S. East Coast and it was relatively
small compared with those in other states (McBride
2000). The expansion of railroads into Florida
increased the value of Florida’s fishery because the
fish could then be readily transported to northern
markets (Brice 1898), and by 1889–1890 the landings
(.0.9 million kg) and value (US$100,000) of Florida’s
shad stocks were higher than those of any other marine
product harvested within the state (Smith 1893).
Landings of Florida’s shad stocks peaked at the turn
of the century at about 1.4 million kg and fluctuated
between 0.09 and 0.4 million kg from the 1920s to the
1960s. Thereafter, commercial landings of Florida’s
shad stocks continued to decline and dropped dramat-
ically to zero in the 1990s (Table 1; Walburg 1960a,
1960b; Walburg and Nichols 1967; Williams and
Bruger 1972; ASMFC 1985; McBride and Richardson
2005).
Landings of Florida’s shad stocks declined during
the last century for a variety of reasons. Although
overfishing has been implicated (Williams and Bruger
1972), commercial landings and effort have both
declined because of shrinking markets for these species
and because of increasingly restrictive netting regula-
tions within Florida. The most recent decline in
commercial landings of Florida’s shad stocks was a
result of netting restrictions that reduced gill-net effort
to zero in the 1990s (McBride 2000).
At the beginning of Florida’s commercial shad
fishery, only gill nets were used (Baird 1874). By the
1900s, fishing methods had expanded to include drift
gill nets, haul seines, and anchored or staked gill nets
(Smith 1898; Stevenson 1899; Walburg and Nichols
1967). In the 1950s, haul seines were the primary gear,
and gill nets were secondary (Walburg 1960a). Today,
netting for shad is no longer a significant commercial
enterprise in Florida. During the early 1970s, haul
seines were discontinued in the St. Johns River
(Williams and Bruger 1972), and by the late 1990s
gill nets were so heavily regulated that they were
virtually eliminated as commercial gear (McBride
2000).
Florida’s commercial shad fishing grounds have
shifted over time as well. In the 1860s, shad fishing
became established near the mouth of the St. Johns
River, between Mayport (river kilometer [rkm] 0;
Figure 1) and Jacksonville, and also farther upstream,
near Palatka (rkm 127; Baird 1874). By the 1950s,
harvest was primarily by set gill nets in the lower river
and by haul seines in the middle river (near Palatka;
Walburg and Nichols 1967). The use of gill nets around
the Mayport jetties had increased by the 1970s, and by
the early 1990s nearly all of the shad harvested came
from gill nets fished in coastal waters just offshore of
Mayport (Williams and Bruger 1972; McBride 2000).
Fishing offshore of Atlantic states other than Florida
(i.e., the ‘‘ocean-intercept’’ fishery) probably added
additional fishing pressure on Florida’s shad stocks. In
the 1980s and 1990s gill-net landings of shad from this
ocean-intercept fishery more than doubled (ASMFC
1999). By 2005, ocean-intercept fishing was phased out
because of concerns that fishing on mixed stocks in the
ocean could be adversely affecting smaller shad stocks,
which were by and large poorly monitored (ASMFC
1985, 1998, 1999; Hoenig et al. 2008).
TABLE 1.—Annual (1987–2005) commercial landings of
anadromous American and hickory shad, combined, from
Florida’s Nassau, Duval, and St. Johns counties (all coastal),
and Putnam county (inland). The geographic area was chosen
to limit misreporting of other species that are commonly called
‘‘shad’’ (i.e., menhadens Brevoortia spp. on Florida’s west
coast and gerreids in south Florida). A fishing year covers the
period from July of one year to June of the next year (e.g.,
1987¼ July 1986–June 1987). Total landings combine ocean
and riverine catches. Source: Florida Marine Fisheries
Information System.
Fishing year Ocean landings (kg) Total landings (kg)
1987 64,557 70,6501988 121,023 121,0791989 74,927 75,0511990 77,219 131,4971991 26,732 32,5421992 22,560 22,6351993 11,138 11,1381994 11,332 11,3491995 12,178 12,2211996 1,659 1,6591997 25 251998 8 81999 218 2182000 364 3642001 0 02002 0 02003 0 02004 0 02005 0 0
1670 MCBRIDE AND HOLDER
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Although sportfishing for shad stocks in the St.
Johns River occurred as early as the late 1800s (Pfeiffer
1975), it was the introduction of spinning tackle in the
1940s that helped popularize shad sportfishing (Snyder
1949; Nichols 1959; Walburg 1960a, 1960b). During
the 1950s and 1960s, the shad sport fishery in the St.
Johns River was estimated to be larger than the shad
sport fisheries in any of the other Atlantic states
(Nichols 1959, 1966; Walburg and Nichols 1967).
Today, most shad in Florida are caught by recreational
anglers practicing catch and release (see Assessment
Update). Fly-fishing for shad in particular has become
popular in Florida (Lindsay 1999). Anglers fishing for
shad use public boat ramps and fish camps on the St.
Johns River between DeLand and Lake Poinsett (rkm
238–378; Walburg 1960a; Branyon 1999; McPhee
2002), traditional access points being found near
‘‘Shad Alley’’ at Cameron Wight Park (rkm 281),
Mullet Lake Park (rkm 285), Lemon Bluff (rkm 290),
Puzzle Lake (accessible from C. S. Lee Park [rkm
310]), and Hatbill Park (rkm 330). The certified state
record fish (a tie) for American shad (2.36 kg) were
caught in the St. Johns River within Seminole and
Volusia counties (Florida Fish and Wildlife Conserva-
tion Commission, floridafisheries.com/record.html).
Regulations.—Commercial fishing regulations for
Florida’s shad stocks have existed since 1896,
including (1) effort restrictions (no fishing on Sundays),
(2) mesh size restrictions (to allow the escapement of
smaller fish), and (3) closed areas (nets prohibited
within inlets and in the lake portions of the St. Johns
River) (Stevenson 1899; Walburg and Nichols 1967).
By 1960, regulations included (1) a commercial season
(November 15 to March 15) and (2) an area closed to
commercial nets south of Lake George (rkm 197). In
the 1990s, a series of mesh size and net-tending
regulations culminating in a net limitation referendum
(Constitution of Florida, article X, section 16) caused
sharp reductions in Florida’s commercial shad landings
and effort (McBride 2000). Consequently, although
sale of American and hickory shad is not prohibited, the
commercial net fishery for shad has been effectively
eliminated within state waters.
Sportfishing for Florida’s shad stocks has been
regulated by bag limits since 1955. In 1973, the initial
bag limit of 15 American shad was lowered to 10 fish/d
(Williams 1996). Since 1990, a saltwater fishing
license has been required of most anglers who fish
for marine species, including anadromous species.
Since 1997, hook and line has been the only allowable
fishing gear for American shad, hickory shad, and
Alabama shad Alosa alabamae, and it has been
unlawful to possess more than 10 fish in any
combination of these species (Florida Administrative
Code, chapters 46–52.001).
Management of all U.S. East Coast shad and river
herring (Alosa) species is overseen by the ASMFC
according to an FMP subscribed to by the individual
Atlantic coast states (ASMFC 1985, 1999). Amend-
ment 1 to the ASMFC’s shad and river herring FMP
calls for (1) a 5-year phaseout of the ocean-intercept
fishery, (2) regulating the in-river fishery at target
exploitation rates, and (3) implementing bag limits of
10 fish/d in the recreational fishery (ASMFC 1999).
Amendment 1 also established monitoring programs
for all states; it requires Florida to monitor commercial
and recreational shad fisheries and to complete fishery-
independent surveys of American shad.
Stock assessments.—Stock assessments of Florida’s
St. Johns River shad stocks were initially limited to
occasional surveys of the fishery and comments from
the public. For example, reports of the 1896 Florida
shad fishery document hundreds of people involved in
the harvest of about 450,000 shad worth about $62,000
(Stevenson 1899). Concerns were expressed over a
century ago that downstream nets ‘‘completely block
the river, and prevent any shad from coming up’’
(Osborn 1882: 351). Also, requests for a hatchery on
the St. Johns River began so that ‘‘the yield should be
increased by artificial means’’ (Henshall 1898:254).
The first scientific assessments of Florida’s St. Johns
River shad stocks began in the 1950s. Talbot and Sykes
(1958) tagged 882 American shad during the 1953
spawning run and had a 21.3% recapture rate. Walburg
(1960a) tagged another 950 American shad during the
1958 spawning run and reported a recapture rate of
12.7%. These data were used to estimate the stock size
of American shad in Florida’s St. Johns River, resulting
in a production of 0.41–1.7 million kg annually
between 1953 and 1965 (Walburg 1960a; 1960b;
Nichols 1964, 1965, 1966a). Stock size during this
period was roughly equal to the peak yields of
Florida’s American shad in the early 1900s. Thus, this
stock was much larger at the beginning of its
exploitation than during the 1950s, the mortality rates
were astonishingly high in the early 1900s, or both.
During the 1950s, when fishing mortality was
reasonably low, management of Florida’s shad stocks
focused on allowing sufficient escapement to maintain
viable fisheries. In the St. Johns River, total biomass
harvest ranged between 15% and 37% of the stock;
depending on the year, about 2–8% were taken by
commercial gill nets, another 7–20% by commercial
haul seines, and 3–8% by hook-and-line sport anglers
(Walburg 1960a, 1960b; Walburg and Nichols 1967;
ASMFC 1985).
Biological studies and descriptions of Florida’s shad
ANADROMOUS SHADS OF FLORIDA 1671
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stocks were also completed by Williams and Bruger
(1972) and Williams et al. (1975). Their studies
provide habitat-based management recommendations
regarding proposed alterations of river flow and
channelization in areas where shad spawn. An updated
review of shad habitat requirements, specifically in
relation to river water levels and flows, was recently
completed by Harris and McBride (2004).
The conservation of shad stocks faced a new
challenge when ocean-intercept landings doubled in
the 1980s and 1990s, eventually accounting for 60% of
the total coastwide catch (ASMFC 1999; Brown et al.
1999; Hoenig et al. 2008). Concern arose that smaller
stocks, particularly those that were not being monitored
closely, were adversely but cryptically affected by this
interjurisdictional fishery. For example, an ASMFC
(1998) stock assessment of shad populations included
assessments of only 12 populations from Maine to
Georgia; no Florida rivers were included because of
insufficient data. Furthermore, efforts to identify
diagnostic characteristics of river-specific or state-
specific stocks failed, so that monitoring the stock
composition from the ocean-intercept fishery’s catch
was of little use in terms of assessing the impact of this
fishery on individual shad stocks (Epifanio et al. 1995;
Brown et al. 1999; ASMFC 1999).
Commercial fishing data have been reported to
Florida’s Marine Fisheries Information System since
1986 (Table 1), when state law required reporting of all
wholesale transactions of marine organisms landed
within Florida. These data represent a census of all
legal commercial landings, but the corresponding catch
rates may be biased because trips that do not catch fish
do not need to be reported. Also, landings are not
separated by shad species, although American shad is
frequently the target species and is generally much
more abundant than hickory shad in Florida. These data
depict the decline of commercial shad landings due to
netting restrictions implemented during the 1990s, but
otherwise, they are of little use for continued
assessment of Florida’s shad stocks.
Recreational landings can be downloaded from the
Marine Recreational Fisheries Statistics Survey
(MRFSS) Web site (http://www.st.nmfs.gov/st1/);
however, no landings of Florida’s shad stocks were
reported to this Web site. Apparently, the MRFSS does
not intersect with the recreational shad fishery on
Florida’s St. Johns River, presumably because this
fishery is concentrated well upstream. Walburg (1960a)
summarized the data from a creel survey of the 1958
American shad sport fishery on the St. Johns River.
This included a riverwide survey of all major fish
camps, seasonality of catch, and numbers of male and
female American shad and hickory shad per week.
Walburg (1960a) also estimated the sport catch from
spawning years 1953–1958. Other estimates of recre-
ational landing were reported in Nichols (1964, 1965),
Walburg (1960b), Williams and Bruger (1972), and
Williams (1996). No biological samples were attempt-
ed during these other surveys except to identify sex in
some instances. In 2000, a pilot access-point creel
survey was implemented by the Florida Fish and
Wildlife Conservation Commission at three public boat
ramps (rkm 281, 285, and 310) during the peak fishing
period (January–March). Only three shad were ob-
served in six sampling days, which led us to conclude
that widely scattered public boat ramps and private
access points, as well as a high incidence of catch-and-
release fishing, confounded such an access-point
survey design. To date, creel surveys had produced
little more than a single point estimate of catch and
effort, precluding much in the way of comparisons
between decades, but we report herein on a multiyear
(1993–2005), roving creel survey that is suitable as a
proxy for following Florida shad stock size.
Life history information has been challenging to
apply to the assessment of Florida’s shad stocks. For
example, there is strong evidence that anadromous
shad return to their native rivers to spawn (Hollis 1948;
Talbot and Sykes 1958; Nichols 1960; Judy 1961;
Leggett and Whitney 1972), but no significant tagging
programs or juvenile surveys have occurred for several
decades, precluding estimates of population size or
stock–recruitment relationships within Florida (Trippel
et al. 2007). Furthermore, in the St. Johns River, there
is no fall line to concentrate fish, and most of the
spawning ground is highly braided, shallow habitat,
which can complicate tag–recapture designs. As
another example, fish size is a simple variable with
which to assess stock status, although it requires
recognition that American shad are larger than hickory
shad and females are larger than male conspecifics
(LaPointe 1957; Walburg 1960a; Leggett 1969;
Williams et al. 1975). Age is a more informative
variable to monitor fisheries, and many shad species
are managed based on mortality benchmarks (i.e., F30
),
which are typically estimated from age data. Nonethe-
less, a validated aging method exists for only one
American shad stock (i.e., the Connecticut River),
which is so geographically distinct that age-based
assessment methods cannot be readily applied to
Florida’s stock (McBride et al. 2005). Even if a
validated aging method existed for Florida’s shad, it is
not clear the data would be helpful for monitoring
mortality: recruitment to the spawning grounds is
incomplete in any particular year and both species are
reported to be relatively short-lived (6–7 years;
LaPointe 1957; Walburg 1960a; Leggett 1969; Wil-
1672 MCBRIDE AND HOLDER
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liams et al. 1975; Harris et al. 2007). Finally, several
estimates of yolked oocyte numbers have been
published (Davis 1957; Walburg 1960a; Leggett
1969; Leggett and Carscadden 1978), but Olney et al.
(2001) concluded that American shad have indetermi-
nate fecundity and asynchronous oocyte development;
therefore these historical estimates cannot be readily
applied to egg production models in Florida (Olney and
McBride 2003).
Methods
Stock assessment data.—As identified above, many
standard assessment approaches (i.e., stock–recruit-
ment, mark–recapture, age-based, or egg production)
are not tractable for assessing the status of Florida’s
anadromous shad stocks at this time. In this data-poor
situation, we turned to a relatively recent but
reasonably long time series of catch per unit effort
data from a creel survey. We also had data from a
recent but shorter time series of electrofishing catch-
per-unit-effort data, which we used to validate the creel
survey data as a proxy for stock size. The electrofishing
survey also supplied information about shad species,
sex ratio, and fish size.
The temporal and spatial extent of sampling (creel
and electrofishing) was based on previous reports of
shad spawning in Florida’s St. Johns River. The
seasonal range of the spawning runs is reported to
occur from November to May (Baird 1874; McLane
1955; Walburg 1960a; Leggett and Whitney 1972;
Williams et al. 1975; Davis 1980; Harris et al. 2007).
Thus, even though the run was typically sampled in
two calendar years, we refer to the most recent year as
that of the spawning run (e.g., the 2002 spawning run
began in 2001 and ended in 2002); this terminology is
compatible with the reporting of spawning runs in
northern states. Our sampling areas were concentrated
in the upper river (i.e., the southern portion),
specifically to target American shad. American shad
spawning grounds are well documented from rkm 230
to rkm 415 based on egg surveys (Walburg 1960a;
Nichols 1966a; Williams and Bruger 1972; Williams et
al. 1975) and the distribution of females in spawning
condition (Glebe and Leggett 1981). Moody (1961)
concluded that hickory shad do not migrate as far up
the river to spawn as American shad, but Harris et al.
(2007) reports evidence (gonad histology) of spatial
overlap in the spawning grounds of the two species in
the St. Johns River.
Electrofishing survey.—Spawning seasonality, hab-
itat distribution, sex ratios, and the sizes of anadromous
shad were determined during a standardized electro-
fishing survey of the upper St. Johns River. Estimates
of abundance from the electrofishing survey were also
compared with independent estimates of abundance
from a longer-term, roving creel survey (see below).
Electrofishing was conducted every 2–3 weeks
throughout the 2002–2005 spawning runs between
the south end of Lake Monroe and the north end of
Lake Harney (approximately rkm 274–307; Figure 1);
this area is referred to as the ‘‘creel area’’ because it
overlaps a roving creel survey area. Electrofishing also
occurred in five other areas: (1) the Wekiva River, a
major tributary entering the St. Johns River at rkm 253
downstream of Lake Monroe, (2) the Puzzle Lake area,
an expansive, shallow portion of the St. Johns River
immediately upstream of Lake Harney and extending
into the diffuse Puzzle Lake region (rkm 308–315), (3)
the Econlockhatchee River, another major tributary that
enters the St. Johns River at rkm 311, (4) a shallow,
braided area of the St. Johns River main stem south of
Lake Cone (rkm 330), and (5) a shallow stretch of the
main stem just north of Lake Poinsett (rkm 378).
Preliminary sampling in these five additional areas
began in 2003, and regular sampling occurred every 3–
6 weeks per area during the spawning runs of 2004 and
2005.
Measures of fish abundance adhered to standardized
procedures. Fish were shocked with pulsed direct
current using either 340 or 680 V and 60 Hz to
standardize power transfer at 10–12 A; the actual
power measured for the 700 transects completed in this
study was 11.4 6 2.1 A (mean 6 SD). The electric
charge was released in a pattern of 25 s on and 5 s off
until a total on-time of 600 s was achieved. Each
transect followed a sinusoidal path in a downstream
direction at a speed of about 2 knots. This meandering
extended from shore to shore, where the width of the
river was less than approximately 50 m. Where the
river was wider, the meandering of each transect
extended between the shoreline and midchannel; to
randomize the sampling locations the initial riverbank
(side) was chosen by a coin toss every 4–5 transects per
day, and the subsequent transects alternated down-
stream from side to side. Two biologists, each with a
long-handled dip net, dipped for shad adults on most
(97.1%) transects; otherwise, only one biologist was
available for netting fish, but this was not considered to
appreciably affect (i.e., lower) the measures of
anadromous shad abundance in those 20 transects.
All transects reported herein were sampled during
daylight hours.
Fish abundance was calculated as a geometric mean
number of fish per transect (GM), based on data from 5
to 10 transects per area per day:
GM ¼ antilog1
n
Xn
i¼1
logeY þ 1;
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where n is the number of transects in a specified fishing
area for a single day and Y is the number of fish dipped
per transect (either American shad, hickory shad, or
both species combined).
All anadromous shads were sampled without
replacement or were marked with a hole punched in
a medial fin so that recaptures were identifiable. Only 3
of 245 marked fish were recaptured, and no further
conclusions were reached regarding these preliminary
mark–recapture efforts. All fish brought back to the
laboratory were measured to the nearest millimeter fork
length (FL) and weighed to the nearest 0.1 g total body
weight. The sex of each fish was determined by
macroscopic inspection of the gonads. Before release,
marked fish were measured for fork length; their sex
was recorded as male if milt was expressed when the
abdomen was squeezed or female if milt was not
apparent (this method was determined to be reliable by
examining unmarked fish in the laboratory; McBride,
unpublished data). A four-way analysis of variance
(ANOVA) was used to determine whether FL varied
significantly as a result of gender, sampling month,
year, or location. A full model was possible for
American shad, but third-order and fourth-order
interactions were not included in the model for hickory
shad because the sample size was too small. Results
were deemed statistical significant at a ¼ 0.05.
Roving creel survey.—A roving creel survey was
used to monitor angler catches of American and
hickory shad during 11 of the 13 spawning runs from
1993 to 2005. Angler interviews and instantaneous
counts of the number of anglers were completed within
an 11.9-km stretch of the St. Johns River between Lake
Jesup and Lake Harney. This creel area was historically
well known for shad fishing and includes such fishing
locations as Shad Alley, Lemon Bluff, and Iron Bend
(Branyon 1999; McPhee 2002). Sampling was strati-
fied by day of the week (weekday versus weekend) and
diurnal period (0730–1230 hours and 1230–1730 hours
before 1997 and 0700–1030 hours, 1030–1400 hours,
and 1400–1730 hours beginning in 1997. Shad fishing
is concentrated on weekends and holidays (Walburg
1960a), so three weekdays and two weekend days were
sampled every 2 weeks. Holidays were counted as
weekend days. Each 2-week period started on a
Monday and ended 14 d later.
Random, equal probability determined whether the
instantaneous count of fishing effort was measured on
the upstream or downstream run. Instantaneous counts
were made of all anglers in all boats within the main-
stem of the St. Johns River between the power lines
across from the boat-launching ramp at rkm 279.7 to
the power lines upstream of Iron Bend at rkm 291.6.
Anglers were interviewed on the complementary run
(i.e., downstream or upstream) and asked what species
they targeted, how many hours they fished, how many
fish they caught (by species or species groups), and
how many fish they kept (by species or species
groups). No fish were sampled for sex or size; in fact,
American shad and hickory shad were recorded only as
‘‘anadromous shad’’ because many anglers cannot
distinguish between these species; blueback herring
Alosa aestivalis, on the other hand, are more readily
identified and are not targeted in the sport fishery, so
they are not mixed in with these catch data.
Catch and effort data from the roving creel surveys
were expanded by using a mean-of-ratios estimator for
incomplete-trip interviews (Hoenig et al. 1997), that is,
Rh ¼1
n
Xn
j¼1
cj
lj;
where Rh
is the mean-of-ratios estimate for the species
in stratum h, cjis the catch in interview j, l
jis the total
angler-hours in interview j, and n is the total number of
interviews in stratum h. This estimate of angling
success included only trips with anglers that said they
were targeting shad, and fishing trips less than 0.5 h
long at the time of the interview were discarded.
Models.—We used a falsification approach to test
four hypotheses regarding the possible positive effects
of the in-state netting restrictions implemented during
the 1990s on St. Johns River shad stocks. The first two
hypotheses were designed to investigate evidence of
size- and sex-selective harvesting effects. In particular,
mesh size of gill nets could be used to select for fish
size, whereas haul seines and hook-and-line gear
cannot inherently be used in this manner (although
females may be preferentially harvested with any gear
because they are bigger and their roe has a high value;
Walburg 1960a). This concern was raised by Williams
and Bruger (1972), who noted that there was a 5.6:1
female : male ratio in landings from the gill nets (;13-
cm stretch mesh) fished near the Mayport jetties in the
early 1970s. They also noted that the sex ratio in the
recreational catch had declined from 1.1:1 in the 1950s
to 0.71:1 and 0.53:1 in 1969 and 1970. Here, we
compared recent data collected by electrofishing with
historical data collected by haul seine or hook and line
to see if size- and sex-selective harvesting effects
continued to exist.
The four hypotheses were as follows:
(1) Fish sizes are not different between decades.
Student’s t-tests were used to test whether monthly
or annual mean fish sizes were different from
historical estimates of mean fork length. No
differences would indicate a stable trend in fish
size, but decreased size in recent years could
1674 MCBRIDE AND HOLDER
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indicate a negative effect of size-selective harvest
practices, and increased size could indicate a
rebuilding trend. These tests were completed
independently for each species and each sex, and
because multiple comparisons were made, signif-
icance was set at 0.01.
(2) Sex ratios are not different between decades.
Historical sex ratios were approximately 1:1, which
are assumed to be optimal. Goodness-of-fit (chi-
square) tests were used to test whether recently
measured shad sex ratios were different from
historical estimates. Sex ratios that are stable
between decades are postulated to be desirable.
Female-biased sex ratios would not be expected, at
least as measured by electrofishing, and strongly
male-biased sex ratios would indicate a negative
effect of size-selective harvest practices. Again,
because multiple comparisons were to be made,
significance was set at 0.01.
(3) Angling success (i.e., angler catch rates) is not
related to fisheries-independent estimates of abun-
dance. This hypothesis was tested by correlating
success (mean-of-ratios estimates from the creel
survey) and geometric mean abundance of shad
collected by electrofishing. This hypothesis is not a
biological question per se but rather a validation
test as to whether the time series of angling success
estimates may be used as a proxy for spawner
abundance. If so, angling success should be
significantly and positively correlated with electro-
fishing abundances during the period both surveys
occurred (2002–2005).
(4) The annual time series trend of angling success is
zero. This hypothesis was tested with regression
analysis of the creel survey abundance time series
for the 1993–2005 spawning runs. If this hypoth-
esis is not rejected, the time series represents no
measurable change in anadromous shad abundance
during this 13-year period. If it is rejected, the time
series may indicate either a decreasing or an
increasing trend in abundance. An increasing trend
would be consistent with the postulate that netting
restrictions and other fishing regulations imple-
mented in the 1990s are helping to increase
Florida’s shad stock abundance. This hypothesis
assumes that catchability remained constant, which
seems reasonable because no innovations in fishing
methods occurred during this period.
Results
Spawning Runs of 2002–2005
American shad adults arrived on the spawning
grounds at the same time as or later than hickory shad
adults (Figures 2, 3). Hickory shad were collected
south of Lake Monroe up to 4 weeks earlier at the
beginning of the 2002 and 2003 spawning runs (i.e., by
mid-December 2001 and early December 2002) than
were American shad (i.e., mid-January 2002 and early
January 2003). Both species were first collected
together during the same week of the 2004 and 2005
spawning runs (i.e., mid-December 2003 and early
January 2005). American shad were present in the river
much longer, until May (Figure 2), whereas hickory
shad were not encountered in sampling areas after
March (Figure 3).
Hickory shad did not migrate as far upstream as
American shad did (Table 2). The Wekiva River, which
represented the most downstream electrofishing loca-
tion, was the only sampling area where hickory shad
were more abundant than American shad. In the creel
survey area, hickory shad were occasionally as
numerous as American shad. American shad were
even more abundant farther upstream. In contrast,
hickory shad adults were present in low or variable
numbers within the Puzzle Lake area and Econlock-
hatchee River, and they were not collected further
upstream.
American shad grew larger than hickory shad
(Figure 4a, c). The longest American shad was 464
mm FL (1,153 g total body weight) and the heaviest
was 1,700 g (450 mm); both were females. The longest
hickory shad was 414 mm FL (995 g) and the heaviest
was 1,027 g (400 mm); both were females. Males were
smaller than females in each species (Figure 4a, c). The
longest male American shad was 423 mm FL (no body
weight measured) and the heaviest was 1,095 g (419
mm). The longest male hickory shad was 400 mm FL
(770 g) and the heaviest was 913 g (373 mm).
The length of American shad was affected by factors
other than species and gender. According to a four-way
ANOVA, American shad fork length varied by sex (P, 0.0001), month (P¼ 0.018), year (P , 0.0001), and
sampling area (P¼ 0.0018); no interactive effects were
significant. Most striking was how American shad were
longer at the beginning of the spawning run than later
in the run. Mean female size was greater than 400 mm
FL in December and January but less than 390 mm by
April and May; mean male size exceeded 355 mm FL
in December and January but was less than 350 mm by
April. In the last 2 years of sampling, females averaged
about 1 cm longer than they were in the first 2 years,
and male size varied without an obvious trend over the
same 4-year period. Lengths of both sexes varied
between sampling areas but without an obvious pattern.
Sex, month, year, and area interacted to affect the
length of hickory shad (secondary interactions, P ,
0.05). Females were longer than males, and average
ANADROMOUS SHADS OF FLORIDA 1675
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female length increased about 2 cm from 2002 to 2005.
Samples sizes were, however, fairly small, and no other
patterns were discernible.
The weight of female American shad declined
steadily and significantly over the spawning season
(Figure 4b). An analysis of covariance that regressed
fish weight linearly on length with period (2-month
intervals) as a covariate showed no significant
interaction between slopes (P¼ 0.26) but significantly
different intercepts between the bimonthly groups (P¼0.001).
The mean sizes of both sexes of American shad were
larger historically (1958) than in recent years (2002–
2005; Figure 5). Mean female lengths were 390, 385,
394, and 402 mm FL in the 2002–2005 spawning runs,
respectively, whereas males averaged 356, 346, 365,
and 349 mm. In the 1958 shad run, the weighted mean
length was 427 mm FL for females and 386 mm for
males (Walburg 1960a). Multiple t-tests of sex-specific
fish size confirmed that these historical size differences
were significantly larger than in recent years (P . 0.01;
for statistical purposes, all eight comparisons assumed
FIGURE 2.—Abundance of American shad within six sampling areas along the St. Johns River, from downstream to upstream:
(A) the Wekiva River, (B) the roving creel survey area (Lake Monroe to Lake Harney), (C) the Econlockhatchee River, (D) the
Puzzle Lake area (Lake Harney to Puzzle Lake), (E) south of Lake Cone, and (F) north of Lake Poinsett. Note the different
scales of the y-axes. The thin vertical lines represent 95% confidence intervals; the numbers atop some error bars give the upper
confidence limit when it is off the scale.
1676 MCBRIDE AND HOLDER
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FIGURE 3.—Abundance of hickory shad within four sampling areas along the St. Johns River, from downstream to upstream:
(A) the Wekiva River, (B) the roving creel survey area (Lake Monroe to Lake Harney), (C) the Econlockhatchee River, and (D)the Puzzle Lake area (Lake Harney to Puzzle Lake). Lake Cone and Lake Poinsett were also sampled but no hickory shad were
collected at those locations. See Figure 2 for additional details.
TABLE 2.—Total numbers of American shad and hickory shad adults collected via electrofishing from spawning runs in the St.
Johns River, by sampling year and location. Sample years cover the period from November of one calendar year to May of the
following year (e.g., 2002¼November 2001 to May 2002). Sampling locations are ordered from north to south (i.e., downstream
to upstream).
Year Sampling locationa American shad Hickory shad Transects sampled
2002 Creel area 56 19 422003 Wekiva River 0 0 3
Creel area 225 29 104Econlockhatchee River 5 0 3N Puzzle Lake 209 3 33N Lake Cone 40 0 10N Lake Poinsett 2 0 6
2004 Wekiva River 4 12 20Creel area 33 36 119Econlockhatchee River 161 8 24N Puzzle Lake 247 2 50N Lake Cone 50 0 21N Lake Poinsett 3 0 18
2005 Wekiva River 2 21 25Creel area 23 18 102Econlockhatchee River 26 10 13N Puzzle Lake 186 3 53N Lake Cone 133 0 30N Lake Poinsett 11 0 24
Total 1,416 161 700
a The creel area extends from the southern end of Lake Monroe to the northern end of Lake Harney.
Some locations are approximate.
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the variance for the 1958 fish equaled the maximum
variance observed in the 2002–2005 spawning runs
because variance was not reported in Walburg 1960a).
Davis (1980) reported modal female sizes of 433 mm
FL for the 1971 and 464 mm for the 1972 spawning
runs (male modes: 401 and 360 mm FL), but he did not
report mean values so no further analyses were
attempted.
No obvious gender differences in hickory shad sizes
were detected between decades. The average hickory
shad lengths measured in 1972 and 1973 fell within the
95% confidence limits of those measured during 2002–
2005 (Figure 5).
Male and female American shad were found together
within all sampling areas, but the sex ratio varied
widely among months (Figures 6, 7). In each year
sampled, more males were collected at the beginning of
the spawning run and more females at the end of the
run. Hickory shad sex ratios did not appear to have a
strong seasonal trend.
The proportion of American shad females (Pf) was
significantly biased for the 2002 (Pf¼ 0.12) and 2003
(0.18) spawning runs (chi-square test; P , 0.001),
whereas the sex ratios for the 2004 (0.52) and 2005
(0.51) spawning runs were not significantly different
from 1:1 (P . 0.1). During the 1958 spawning run,
female American shad were significantly more abun-
dant than males (P , 0.001); however, the value of Pf
(0.53) was close to 0.5, and its significance seemed to
have been influenced by the particularly large sample
size of 63,693 (data from Walburg 1960a).
The sex ratios of hickory shad were significantly
different from 1:1 in each of the years 2002–2005 (P ,
0.01) and actually declined over time, from 0.27 to
0.32, 0.16, and 0.15. This is the opposite of the pattern
that was observed for American shad during this same
period, and it differs significantly from the historical
ratios for hickory shad. During the 1958 spawning run,
hickory shad were significantly biased toward females
(chi-square test: N¼ 1,553, Pf¼ 0.56, P , 0.001; data
from Walburg 1960a); during the 1972 and 1973
spawning runs the sex ratios (pooled for both years)
were not different from 1:1 (N ¼ 118, Pf¼ 0.54, P .
0.1; data from Williams et al. 1975).
Sport Fishery in 1993–2005
The estimated sport catch of shad within the 11.9-km
creel survey area ranged from 1,270 to 12,600 fish/
year, averaging 5,880 fish/year (SD ¼ 3,680). These
estimates were calculated over 13 years (1993–2005
but excluding 1997 and 2000) for the 20-week periods
beginning in early December and ending in late April.
Over the entire 13-year period, both catch and effort
declined (Figure 8). In average or poor sportfishing
FIGURE 4.—Scattergram of total body weight versus fork
length for American and hickory shad collected by electro-
fishing in the upper St. Johns River (Wekiva River to Lake
Poinsett) during the 2002–2005 spawning runs. The middle
panel shows time-varying data: December–January (plus
signs), February–March (dots), and April–May (times signs).
Data for all sample areas and years are combined.
1678 MCBRIDE AND HOLDER
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years, angling success was below 1.0 shad/h, whereas
in better years it was above 1.0 shad/h (Table 3; Figure
9).
Catch and release was commonly practiced; 79% of
the shad caught by angling in the 2002 spawning run
were released, along with 77% in 2003, 71% in 2004,
and 79% in 2005. Although some anglers may release
hickory shad preferentially, it is more common for
anglers to release males and keep females regardless of
species. Anglers fishing for freshwater fish, particularly
black crappie Pomoxis nigromaculatus, also caught
American shad; this could add to the total harvest rate
but was not calculated here.
A statistically significant and positive relationship
was found between the shad abundance measured by
electrofishing and that measured by the roving creel
survey (Figure 10). This was observed when the creel
survey estimates were correlated to electrofishing
within either the creel area (i.e., Lake Monroe to Lake
Harney: r ¼ 0.41, N ¼ 39, P ’ 0.01) or within an
adjacent, upstream section (Lake Harney to Puzzle
Lake: r¼0.69, N¼16, P , 0.01). Thus, the time series
of angler catch rates was an appropriate proxy for
measuring annual variation in population size.
The linear trend of angling success for the period
1993–2005 was not statistically different from zero
(Figure 9). During this period, angler success rates
have fluctuated without trend around 1 shad/h in the
creel survey area. These relatively stable estimates of
success have occurred during a period of generally
declining effort in the recreational shad fishery (Figure
8).
Discussion
Spawning Runs
American shad are winter spawners in Florida.
Although we did not collect any American shad on
the spawning grounds before December, they are
reported to enter the St. Johns River in November in
association with declining water temperatures (Wal-
burg 1960a; Leggett and Whitney 1972). We observed
only a single peak in fish abundance, generally during
February, which was also reported by Williams et al.
(1975) for the 1972 spawning run. In contrast,
Williams et al. (1975) and Davis (1980) reported two
peaks in abundance during some spawning runs of the
early 1970s. Davis (1980) noted that males predomi-
nated the first peak in abundance, and he suggested that
FIGURE 5.—Mean fork length of shad in the St. Johns River during different decades. Triangles depict American shad data for
1958 (from commercial haul seines as reported in Table 15 of Walburg 1960a) or hickory shad data in 1972–1973 (from
commercial haul seines as reported in Table 2 of Williams et al. 1975); diamonds depict electrofishing data for 2002–2005, the
thin vertical lines representing 95% confidence intervals. The American shad data are monthly means, the hickory shad data
means by sampling date.
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a second peak was milling or run-back behavior that
increased catchability. Florida’s American shad do not
appear to spawn in more than 1 year, a postulation
based on a lack of a downstream migration (Stevenson
1899), the absence of spawning marks on their scales
(LaPointe 1957; Walburg 1960a; Leggett 1969), and
energetic evidence (Glebe and Leggett 1981). Thus, the
decline in American shad abundance during spring
represents mortality rather than migration out of the
river.
Hickory shad are also winter spawners, but they are
found in the St. Johns River for a shorter period and do
not migrate as far upstream as American shad. They
have been collected by early December (Walburg
1960a; Williams et al. 1975; Harris et al. 2007) and
inhabit more of the lower St. Johns River, including
‘‘deeper waters of Lake George’’ (Moody 1961:13).
Our sampling appears to have adequately captured the
seasonality of the hickory shad spawning run, but
future investigations of this species should include a
larger part of the lower river. Hickory shad are thought
FIGURE 6.—Monthly proportions of female American shad
and hickory shad collected by electrofishing in the upper St.
Johns River (Wekiva River to Lake Poinsett) during the 2002–
2005 spawning runs. Months in which fewer than 10 fish of a
species were collected were excluded.
FIGURE 7.—Proportions of female American shad and
hickory shad during the spawning run in the St. Johns River
during different historical periods: 1958 (census card survey
of anglers from Table 6 in Walburg 1960a), 1972 and 1973
(haul seine collections between the towns of Palatka and
Welaka from Table 2 in Williams et al. 1975), and 2002–2005
(electrofishing collections). Months in which fewer than 10
fish were collected were excluded.
FIGURE 8.—Time series of total estimated recreational
catches (filled boxes) and fishing effort (open boxes) for
anglers targeting the St. Johns River spawning runs of
American and hickory shad, as derived from a creel survey
in the upper river during 1993–2005. The two species are
combined because many anglers cannot distinguish them and
simply target ‘‘shad.’’ The data are a subset of the seasonal
data (periods 3–8, or approximately January to March), when
catch and effort are highest; the trends based on other 2-week
aggregates (i.e., periods 1–10) did not differ (see Table 3 for
specific periods in three representative years).
1680 MCBRIDE AND HOLDER
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to be iteroparous in Florida (Harris et al. 2007), so their
declining seasonal abundance in early spring represents
a migration back to sea after spawning, as well as
natural and fishing mortality.
Status of the Fishery
Florida’s anadromous shad fishery has become
dominated by recreational angling, and most American
and hickory shad caught in the upper St. Johns River
are released. The total estimated catch for the creel
survey area did not exceed 12,600 for any year during
1993–2005, and the catch currently appears to be at
historic lows (1,270 in 2004–2005). Walburg (1960a)
recorded 65,246 American and hickory shad caught
recreationally during the 1958 spawning run, and
Williams and Bruger (1972) reported a catch of 21,300
shad at a single fish camp in 1970. Walburg (1960a)
also reported an average catch rate of 5 shad/angler-
day, and Williams and Bruger (1972) reported 4.5
shad/angler-day. If 3–4 h is typical for a day of shad
fishing, then catch rates during the 1950s and 1970s
ranged from 1.1 to 1.7 shad/h. In contrast, catch rates
during 1993–2005 were greater than 1.0 shad/h in only
3 of 11 years (range, 0.43–1.29 shad/h). Thus, the
TABLE 3.—Estimates of fishing effort (angler hours directed at shad), catch (combined number of American and hickory shad),
and success (shad/h) in a creel survey area on the St. Johns River during three representative spawning runs: 1994–1995 (an
average year), 1998–1999 (the highest-catch year), and 2004–2005 (the lowest-catch year). The sample size for effort (NE) is the
number of sample days with interviews, that for catch (NC) is the number of all interviews reporting at least 0.5 h fished, that for
success (NS) is the number of interviews with shad-directed effort reporting at least 0.5 h fished. Asterisks indicate the 2-week
periods referred to as periods 1–10 in each creel survey.
Sample date
Effort Catch Success
NE
Hours fished SE NC
Number of shad SE NS
Shad/h SE
Calendar years 1994–1995
Nov 3–16 5 0 9 0Nov 17–30 1 0 1 0Dec 1–14*Dec 15–28* 2 109 4 38 1 0.50Dec 29–Jan 11* 5 213 20 129 8 0.73Jan 12–25* 5 821 31 449 23 0.49Jan 26–Feb 8* 5 1,089 41 423 32 0.44Feb 9–22* 4 1,057 30 733 22 0.80Feb 23–Mar 8* 5 3,105 88 2,400 73 0.79Mar 9–22* 5 1,198 65 919 25 1.01Mar 23–Apr 5* 4 473 40 275 8 0.53Apr 6–19* 4 24 73 0 1 0.00Apr 20–May 3 5 0 81 0Total 50 8,089 483 5,366 193 0.71
Calendar years 1998–1999
Dec 4–17*Dec 18–31*Jan 1–14* 4 338 150 22 660 340 6 1.34 0.61Jan 15–28* 5 2,672 511 91 3,419 676 42 1.17 0.11Jan 29–Feb 11* 5 2,175 522 58 3,304 823 24 1.57 0.22Feb 12–25* 5 2,116 635 62 1,722 589 31 0.99 0.11Feb 26–Mar 11* 5 1,490 319 55 2,392 752 25 1.36 0.33Mar 12–25* 4 522 95 42 511 332 10 0.93 0.18Mar 26–Apr 8* 5 181 99 60 98 66 3 0.47 0.12Apr 9–22* 4 25 21 36 0 0 1 0.00Total 37 9,518 1,039 426 12,106 1,509 142 1.20 0.09
Calendar years 2004–2005
Nov 29–Dec 12* 3 0 0 1 0Dec 13–26* 5 0 0 10 0 0Dec 27–Jan 9* 5 63 47 13 35 35 3 1.49 1.49Jan 10–23* 3 76 61 14 25 19 1 0.38Jan 24–Feb 6* 4 865 446 31 466 176 12 0.53 0.11Feb 7–20* 4 530 355 20 454 190 8 0.76 0.25Feb 21–Mar 6* 4 262 160 21 221 194 5 0.36 0.29Mar 7–20* 5 14 10 18 68 37 1 0.50Mar 21–Apr 3* 5 0 0 22 0 0Apr 4–17* 5 0 0 13 0 0Apr 18–May 1 4 50 36 14 0 0 1 0.00Total 47 1,860 598 177 1,270 328 31 0.63 0.16
ANADROMOUS SHADS OF FLORIDA 1681
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populations of American shad and hickory shad in
Florida’s St. Johns River can best be described as low
but stable.
McBride (1999, report to the Atlantic States Marine
Fisheries Commission on an American shad fishing
and recovery plan) had proposed that a sustained or
increasing catch rate greater than 1.0 fish/h during
2002–2005 would be sufficient for concluding that
Florida’s shad stocks benefited from netting regulations
implemented in the 1990s. It was predicted that the in-
state netting regulations implemented in the 1990s
would allow increased passage of shad—particularly
larger spawning females—into the St. Johns River.
However, the findings of this study offer no evidence
that shad stock size increased during the period 1993–
2005, and the fish sizes and sex ratios that we found
suggest continued effects of historical gill-netting
practices.
These data do not, however, lead us to conclude that
there have been no benefits from the 1990s netting
restrictions in Florida. First, the in-state restrictions
were aimed at other species, such as striped bass
Morone saxatilis within the St. Johns River and striped
mullet Mugil cephalus in coastal waters, and in fact, the
fishing mortality of striped mullet has decreased since
the 1990s, with concomitant increases in catch rates
and spawning stock biomass (Mahmoudi 2005).
Second, there may be benefits to anadromous shad
stocks, but the data-poor nature of this stock assess-
ment did not reveal this unequivocally. For example,
the sudden shift in American shad sex ratio between
2002 and 2003 and 2004–2005 was an encouraging
trend, but this was not accompanied by increases in
either geometric mean abundance estimates or angling
success estimates. Concerns about size-selective fish-
ing mortality had emerged as early as the 1970s, when
Williams and Bruger (1972:35) concluded ‘‘that heavy
fishing pressure, especially for female shad, may have
contributed to a decrease in population size.’’ We also
expressed concern at the onset of our study over the
potential for size-selective fishing effects, but at the
FIGURE 9.—Time series of annual mean recreational catch
rates (fishing success) of American and hickory shad
combined in the creel survey area of the St. Johns River
during 1993–2005. The slope of the relationship between
fishing success and year (y ¼ �0.0099x þ 20.5) was not
significantly different from zero (P . 0.05). The data
presented here are for periods 3–8, or approximately January
to March of each fishing year, when catch rates are highest;
the results based on other 2-week aggregates (i.e., periods 1–
10) did not differ.
FIGURE 10.—Scattergrams of the mean geometric abun-
dance of American and hickory shad in the St. Johns River
determined by electrofishing versus the combined shad fishing
success during the same 2-week period in each of 4 years
(2002–2005). Fishing success was measured by a creel survey
between Lake Monroe and Lake Harney, whereas electrofish-
ing abundance was measured (n¼ the number of independent
estimates) in (A) the creel area and (B) the Puzzle Lake area
from Lake Harney to the north end of Puzzle Lake. The
relationship between fishing success and electrofishing rates
was significantly and positively correlated in both examples
(P , 0.01).
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same time we recognized that it is difficult to interpret
changes in size structure to be solely the effect of
fishing (Marshall and McAdam 2007). Nonetheless,
the dramatically smaller shad sizes observed in some
years can lead to much smaller fishery yields (Law
2000), and the smaller sizes and reduced proportions of
females can lead to reduced egg production and
potentially to recruitment limitation (Olney and
McBride 2003).
Perhaps more time is necessary for the benefits to
become apparent. In the course of this study, the effect
of in-state netting regulations had only a decade to
demonstrate an effect. Moreover, ocean-intercept
fishing continued during this period. The effects of
this ocean-intercept fishery have been recognized
elsewhere, such as in the Hudson River, where during
the early 1990s the mean age and incidence of repeat
spawning among American shad started to decline
(Limburg et al. 2003). Although it is unclear how much
time will be necessary to reverse these effects, the most
recent coastwide American shad stock assessment
showed no immediate benefits from the phaseout of
the ocean-intercept fishery (ASMFC 2007). For striped
bass, which is also managed by the ASMFC, rebuilding
took over a decade following severe catch reductions in
1981 (Richards and Rago 1999). So, if the ocean-
intercept fishery had accounted for a significant
amount of mortality on Florida’s anadromous shad,
then more years (i.e., 1–2 shad generations or until
2010–2015) may be needed before benefits are realized
by these stocks in the St. Johns River.
Continued monitoring is desirable to document the
dynamics of the abundance, sex ratios, and sizes of
Florida’s anadromous shad stocks. The current
ASMFC monitoring requirements will satisfy most of
these data needs (ASMFC 1999). Still, the recreational
creel survey may lose its value as a monitoring tool if
recreational fishing effort continues to decline. Fortu-
nately, a suitable baseline of fishery-independent data
has been established with the electrofishing survey,
which will increase in value over time.
Alternative Hypotheses
The patterns of bycatch would be very relevant to
the assessment of various fisheries. There are no
studies of release mortality by Florida’s in-river
recreational fishery, and more research and education
is critical because so many anglers practice catch-and-
release fishing. Although the ocean-intercept fishery
targeting shad has been closed, nontargeted shad
mortality in coastal and ocean nets may still be
important. Documentation of shad bycatch and live
release by other states with active coastal net fisheries
is important in this regard.
Further efforts to rebuild Florida’s shad stocks
should proceed within a comprehensive framework,
one that considers more than the potential fishing
effects. More research on wildlife interactions is
needed to understand the trophic linkages between
Florida’s shad stocks and nonhuman predators (Will-
son and Halupka 1995). Obvious in-river predators on
Florida shad stocks are the osprey Pandion haliaetus,
longnose gar Lepisosteus osseus, and American
alligator Alligator mississippiensis. In addition, the
introduction of armored catfishes (e.g., Callichthyidae
and Loricariidae) to the St. Johns River—species that
feed indiscriminately on benthic prey (Mol 1995)—
raises concerns about new sources of predation on the
eggs of anadromous fishes; these nonnative catfishes
have recently extended their distribution to the shad
spawning grounds, and at least one species (brown
hoplo Hoplosternum littorale) supports an artisanal
fishery (Johnson 2003). How these trophic linkages
affect anadromous shad population dynamics is poorly
understood.
During 2002–2005, visible ulcerations of the
epidermis and underlying tissue were observed in
9.9% of American shad and 3.0% of hickory shad.
Although anecdotal accounts indicate that ulcerated
shad are not new, the causes, dynamics, and conse-
quences of these pathological phenomenon are poorly
understood (Sosa et al. 2007). For example, these
ulcerations could be due to the stress of a long,
energetically costly upstream migration. In general, it
has been noted that Florida’s shad stocks are at the
southern range of both species, and, therefore, may be
thermally stressed. Moreover, it is interesting that the
American shad, which migrates farther upstream and is
semelparous, had a higher incidence of ulcers, which
would support this hypothesis.
Temperature fluctuations affect the migratory pat-
terns of anadromous shad (Quinn and Adams 1996). In
Florida, where American and hickory shad are at their
southern distributional limit, coastal temperatures need
to cool sufficiently to facilitate coastal migration to
northeast Florida and entry into the St. Johns River.
According to Keller et al. (2006), coastal surface
temperatures have cooled to 15.08C by December in
recent years, well within the range of temperatures with
which shad are associated (Leggett and Whitney 1972).
Thus, a thermal bottleneck is probably not preventing
shad from entering the St. Johns River.
Nonetheless, other environmental variations may be
affecting anadromous shad in the St. Johns River. For
example, during the course of our monitoring (1993–
2005), unusually heavy rains from at least one major El
Nino–Southern Oscillation event occurred (1997–
1998; Patterson et al. 2004), which was followed by
ANADROMOUS SHADS OF FLORIDA 1683
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2 years of drought conditions. Moreover, increased
rainfall associated with the Multidecadal Oscillation
has occurred in the past decade (Delworth and Mann
2000). Water flow can affect the survival of anadro-
mous shad eggs and larvae (Williams and Bruger
1972), and river flow rates may be particularly
important in the St. Johns River because it is a low-
flow river that lacks a fall line. Williams and Bruger
(1972:35) noted that ‘‘most spawning occur[s] in
currents of 1–1.5 ft/s [;0.30–0.45 m/s] where there
is a clean sand bottom less than 4 m in depth.’’
Competing demands for water resources, which include
human and wildlife and fisheries needs, are increasing.
Preservation of sufficient water quality, flows, and
levels will certainly continue to be important for
maintaining anadromous shad stocks in the St. Johns
River in the future.
Acknowledgments
This research was a collaborative effort between the
Florida Fish and Wildlife Conservation Commission
(FWC) laboratories at St. Petersburg and DeLeon
Springs. Many other individuals from the FWC assisted
with this special team project; in particular, we thank G.
Chandler, B. Coleman, F. Cross, R. Davis, B.
Eisenhauer, M. Guy, J. Harris, R. Hyle, J. Jenkins, P.
Korpas, E. Lundy, K. Maki, G. Nelson, C. Paxton, A.
Richardson, D. Van Genechten, S. Whitaker, and J.
Wren. We also thank A. Ross (University of Tampa) for
assistance, and L. Connor for providing user-friendly
software for estimating angling success. C. Mundy (St.
Johns River Water Management District), R. Collaro,
and K. O’Keife helped produce Figure 1 and determine
the river distances. N. Trippel and R. Hyle provided
helpful reviews of an earlier draft. The primary source
of funds for this research was the U.S. Fish and Wildlife
Service (Federal Aid in Sport Fish Restoration project
F-106). Other funding came from the State of Florida’s
Marine Research Conservation Trust Fund, the Atlantic
States Marine Fisheries Commission, and the St. Johns
River Water Management District (contract
SG346AA). We thank all of them.
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