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Osmoregulatory capabilities of the gray snapper, Lutjanus griseus: salinity challenges and field observations


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We investigated the osmoregulatory responses (plasma osmolality and blood hematocrit) displayed by the gray snapper 6–192 h after abrupt changes in ambient salinity. Fish were challenged with six different salinity treatments including a control (0, 5, 30, 50, 60, and 70 ppt) and blood samples were collected at various time points post-transfer. Gray snapper across all size classes tested (13.5–24.5 cm total length) acclimated successfully to hypo- and hyper-saline environments (0–60 ppt) after an adjustment period of ∼96 h. However, abrupt transfers to 70 ppt resulted in 100% mortality within 48 h. Laboratory results were then compared with field measurements obtained after fish were captured in low salinity (0–4 ppt) or marine (∼30 ppt) habitats, suggesting that osmoregulatory processes occurred similarly in both settings. Overall, findings suggest that gray snapper possess similar or higher osmoregulatory capabilities compared to many euryhaline species examined to date, and thus should be considered a euryhaline species.
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Osmoregulatory capabilities of the
gray snapper, Lutjanus griseus: salinity
challenges and field observations
Xaymara Serrano a , Joseph Serafy a b & Martin Grosell a
a Division of Marine Biology and Fisheries, University of Miami,
Rosenstiel School of Marine and Atmospheric Science, 4600
Rickenbacker Causeway, Miami, FL 33149, USA
b Southeast Fisheries Science Center, National Marine Fisheries
Service, 75 Virginia Beach Drive, Miami, FL 33149, USA
Available online: 15 Jun 2011
To cite this article: Xaymara Serrano, Joseph Serafy & Martin Grosell (2011): Osmoregulatory
capabilities of the gray snapper, Lutjanus griseus: salinity challenges and field observations, Marine
and Freshwater Behaviour and Physiology, 44:3, 185-196
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Marine and Freshwater Behaviour and Physiology
Vol. 44, No. 3, May 2011, 185–196
Osmoregulatory capabilities of the gray snapper, Lutjanus griseus:
salinity challenges and field observations
Xaymara Serrano
*, Joseph Serafy
and Martin Grosell
Division of Marine Biology and Fisheries, University of Miami, Rosenstiel School of Marine
and Atmospheric Science, 4600 Rickenbacker Causeway, Miami, FL 33149, USA;
Southeast Fisheries Science Center, National Marine Fisheries Service,
75 Virginia Beach Drive, Miami, FL 33149, USA
(Received 30 January 2011; final version received 25 April 2011)
We investigated the osmoregulatory responses (plasma osmolality and
blood hematocrit) displayed by the gray snapper 6–192 h after abrupt
changes in ambient salinity. Fish were challenged with six different salinity
treatments including a control (0, 5, 30, 50, 60, and 70 ppt) and blood
samples were collected at various time points post-transfer. Gray snapper
across all size classes tested (13.5–24.5 cm total length) acclimated
successfully to hypo- and hyper-saline environments (0–60 ppt) after an
adjustment period of 96 h. However, abrupt transfers to 70 ppt resulted in
100% mortality within 48 h. Laboratory results were then compared with
field measurements obtained after fish were captured in low salinity
(0–4 ppt) or marine (30 ppt) habitats, suggesting that osmoregulatory
processes occurred similarly in both settings. Overall, findings suggest that
gray snapper possess similar or higher osmoregulatory capabilities
compared to many euryhaline species examined to date, and thus should
be considered a euryhaline species.
Keywords: tolerance; osmoregulation; gray snapper; Lutjanus griseus;
acclimation; euryhalinity; Everglades restoration
Salinity acclimation is a complex process that involves a set of physiological
responses in multiple osmoregulatory organs (i.e. gills, intestine, and kidneys; Lin
et al. 2004; Marshall and Grosell 2005), and is known to induce changes in
parameters such as plasma osmolality (e.g. Crocker et al. 1983; Nonnotte and
Truchot 1990; Varsamos et al. 2002), Na
-ATPase activity (e.g. Jensen et al.
1998; Arjona et al. 2007), and blood hematocrit (e.g. Leray et al. 1981; Brown et al.
2001; Denson et al. 2003), among others. To date, much of the work on acute
osmoregulatory responses of fish to salinity change has been conducted on
euryhaline species that either encounter different salinity levels in their habitat or
move among distinct habitats throughout their life history (e.g. salmonids).
Typically, these responses begin with a ‘‘crisis’’ period characterized by an increase
or decrease in plasma osmolality, followed by a ‘‘regulatory’’ phase as ions reach
*Corresponding author. Email:
ISSN 1023–6244 print/ISSN 1029–0362 online
ß2011 Taylor & Francis
DOI: 10.1080/10236244.2011.585745
Downloaded by [University of Miami] at 13:40 13 December 2011
steady-state levels, usually within 2 weeks post-transfer (e.g. Ferraris et al. 1988;
Mancera et al. 1993; Arjona et al. 2007); unless acclimation to the new salinity level is
unsuccessful. These phases occur because to counteract the large passive forces that
dominate ion and water movement in the ‘‘crisis’’ period, the permeability of plasma
membranes and tight junctions must be altered, and ion uptake (or extrusion)
systems must be activated during the ‘‘regulatory’’ phase (Ferraris et al. 1988).
Estuaries are generally characterized by wide salinity fluctuations over short time
scales that may vary seasonally with rainfall, river discharge, tidal fluctuations,
evaporation (Tabb and Manning 1961) and/or anthropogenically-driven alterations
of freshwater flow (Wakeman and Wohlschlag 1983; Serafy et al. 1997). As a result,
the success of many species that are either facultative or obligate users of estuaries
may depend on the species-specific capacity to tolerate changes in body fluid
osmolality, osmoregulate and/or engage in more immediate behavioural responses
(Serafy et al. 1997; Serrano et al. 2010). The expectation is that species with juvenile
stages that inhabit estuaries (e.g. Sciaenidae) will be efficient osmoregulators
(Varsamos et al. 2005). In contrast, species with juvenile stages that prefer more
stable salinity regimes are expected to show more limited osmoregulatory abilities
(Dall 1981). Further, while working in Louisiana estuaries, Yokel (1966) contended
that young individuals from different species tended to be more tolerant of low
salinities, whereas adults were less dependent on estuarine areas (spent more time at
sea), and therefore, were expected to be more tolerant of high salinities.
Gray snapper Lutjanus griseus, a species of high economic and ecological
importance in South Florida, USA (Tilmant 1989; Burton 2001; Denit and
Sponaugle 2004; Serafy et al. 2007), is characterized as an estuarine transient
(Ley et al. 1999), but has been included in a list of species that are marine as adults,
but euryhaline as larvae and juveniles (Tabb et al. 1962; Beck et al. 2001). While
juveniles occupy a variety of nearshore habitats with relatively low salinities
(down to freshwater), adults are predominantly marine, but also frequent estuaries
and nearshore habitats, particularly to feed (Starck and Schroeder 1970; Chester and
Thayer 1990; Serafy et al. 2003; Wuenschel and Martin 2006). It is then expected that
as the gray snapper performs inshore–offshore migrations throughout its life span,
the change in external salinity results in physiological (osmotic) stress. Ley et al.
(1999) reported the most extensive salinity range for gray snapper across all sizes
(0–60 ppt) and Rutherford et al. (1989) the highest salinity (66.6 ppt); however, these
values were based strictly on field observations. Serafy et al. (1997), however,
reported that juvenile gray snapper (7.3–8.2 cm total length, TL) survived a brief
(24 h) exposure to freshwater with 0% mortality in the laboratory, but this study
only examined survival and did not target larger size classes, especially those that are
vulnerable to hook-and-line fishing. This information is relevant for gauging
downstream effects of Florida Everglades Restoration (focused on changing the
quantity, quality and timing of freshwater flow in the region; Serafy et al. 2007),
since adults have been suggested to be less tolerant of salinity fluctuations than
younger fish (Starck 1964; Starck and Schroeder 1970).
The main objective of this study was to advance the current understanding of the
basis and limits of the gray snapper euryhalinity. This constitutes the first assessment
of the acute osmoregulatory responses following salinity change of a reef fish, using
size classes that are directly vulnerable to hook-and-line fishing. Overall, we used a
combination of laboratory and field observations on gray snapper to: (1) characterize
the osmoregulatory responses following changes in environmental salinity;
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(2) determine its limits of salinity tolerance; and (3) assess potential differences
associated with the size class of fish tested. For gray snapper to be considered a truly
euryhaline species, we expected transient or no osmoregulatory disturbances in plasma
osmolality and/or blood hematocrit after transferring fish from seawater to various
hypo- and hyper-saline media. In addition, we expected responses to be unrelated to
fish size. Finally, fish collected in the field were expected to display plasma osmolalities
not significantly different from fish in the laboratory at similar salinities. As such, this
is the first ever attempt to compare osmoregulatory laboratory measurements with
field results obtained directly after fish capture.
Materials and methods
Experimental animals
Subadult and adult gray snapper ranging from 13.5 to 24.5 cm TL were collected
from nearshore marine (30–34 ppt) habitats within Biscayne and Florida Bays using
hook-and-line fishing gear. Upon collection, fish were transported to the laboratory
in coolers and held in outdoor tanks with flowing, aerated seawater for a period of
2–3 weeks prior to experiments. Water temperature and salinity in the tanks
averaged 27.8C and 31.5 ppt. Live juvenile pink shrimp Farfantepenaeus duorarum
were provided as food, three times per week (3% body weight per feeding).
Experimental protocol
Five different salinity treatments were chosen to encompass the widest known range
reported for this species. The treatments were 0, 5, 30 (full-strength seawater), 50,
and 60 ppt. A sixth treatment was selected (70 ppt) outside the range reported for this
species to test for an upper lethal salinity limit. Individuals maintained in full-
strength seawater (30 ppt) throughout the duration of the experiment were
considered the control group. Elevated salinities were achieved by addition of
natural sea salts (Instant Ocean mix) to seawater, while lower salinities were
established by adjusting a mix of seawater and dechlorinated Miami city tap water to
the desired salinity. In all cases, transfer of fish to various salinities was completed
within 10 min. To avoid crowding stress, disease or mortality associated with high
ammonia levels, fish were randomly sorted and transferred individually into 30 L
aquaria equipped with biofilters and aeration. Fish were starved for 24 h before and
after transfers, after which feeding was resumed according to the schedule described
above. Fecal matter and other debris were siphoned from tanks 1 day after feeding
and a 25% volume water change was performed at 48, 96, and 144 h. Prior attempts
to draw multiple blood samples from the same individuals over time resulted in
excessive mortalities, especially at extreme salinities. Therefore, individual fish were
sampled only once per salinity treatment as described below. Table 1 presents the
number and size range of fish sampled at each time point within each salinity
Sample collection from abrupt transfers
Fish were lightly anesthetized with a 0.1 gL
MS-222 (3-aminobenzoic acid ethyl
ester, Argent Labs) prior to blood sampling. One fish from each salinity treatment
Marine and Freshwater Behaviour and Physiology 187
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was sampled at 6, 24, 48, 96, and 192 h post-treatment by caudal puncture using a
1 mL heparinized syringe fitted with a 21 gauge needle. Approximately 200–400 mL
of blood was obtained from each fish, a portion of which was extracted into 75 mL
capillary tubes for hematocrit determination. The capillary tubes were centrifuged
for 3 min and the volume of red blood cells was then measured as a percentage. The
rest of the sample was then centrifuged at 16,000gto separate plasma and stored at
20C until analysis. Plasma osmolality was measured using a Wescor Vapro 5520
vapor pressure osmometer (Wescor Inc., Logan, UT). Treatment water osmolality
was also determined as reference values (Table 1).
Sample collection in the field
Using the same methods described above, additional fish were sampled in the field
within 15 min of capture by hook-and-line. Salinity at each capture site was recorded
Table 1. Number and size ranges (TL) of fish sampled at each time point within each salinity
treatment (ppt)
(mOsm kg
Sample time
point (h) N
Fish size
range (cm)
0 25 6 7 13.5–20.5
24 7 14.5–24.5
48 6 14.0–21.0
96 5 14.5–22.5
192 6 13.5–21.0
5 143 6 6 14.0–20.5
24 6 14.5–21.0
48 6 14.0–20.0
96 6 14.3–21.0
192 6 14.0–22.0
30 (control) 934 6 6 14.3–22.5
24 8 16.0–21.5
48 8 16.0–24.0
96 7 15.5–19.0
192 6 16.0–24.0
50 1522 6 6 14.7–21.5
24 6 14.5–22.5
48 6 15.5–21.5
96 6 17.5–21.0
192 6 17.5–20.5
60 1857 6 6 13.5–23.0
24 6 14.3–16.7
48 6 19.0–21.5
96 6 13.5–15.5
192 5 15.5–22.5
70 2150 6 6 16.5–22.0
24 6 15.0–23.0
Notes: Individual fish were sampled only once at any given time point.
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using a calibrated refractometer. This approach was used to compare plasma
osmolalities obtained in the laboratory after abrupt transfer with values observed in
fish in low salinity (0–4 ppt) versus marine (30 ppt) habitats.
Data analysis
Examination of data indicated normality and homogeneity of variances; thus
laboratory and field values were reported as means 1 standard error. The
significance of differences among salinities was determined using one-way
ANOVA, with salinity as the main factor. When statistical significance was revealed
(i.e. P50.05), a Dunnet’s post hoc test was used for multiple comparisons of the
means. Finally, backward stepwise regression was used to evaluate the possible effect
of fish size in relation to plasma osmolality and salinity treatment.
Abrupt transfers
Overall, no mortalities occurred in fish from salinity treatments ranging from 0 to
60 ppt; however, all fish exposed to 70 ppt died within 48 h of transfer. Mean plasma
osmolalities (Figure 1) ranged from 269 to 475 mOsm kg
for fish transferred to
salinities from 0 to 60 ppt, consistent with ranges observed in many other fresh,
estuarine and marine teleosts (260–400 mOsm kg
; Varsamos et al. 2005).
Figure 1. Changes in plasma osmolality for gray snapper Lutjanus griseus following abrupt
transfer to different experimental salinities. All fish exposed to 70 ppt died within 24–48 h
post-transfer. Asterisks correspond to significant statistical differences with respect to controls
(P50.05; analysis of variance and Dunnet’s post hoc comparison test).
Marine and Freshwater Behaviour and Physiology 189
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In control fish (30 ppt), osmolality was maintained at 367 1.32 mOsm kg
(n¼35). In transfers to treatments between 5 and 50 ppt, plasma osmolality was
maintained at levels very similar to controls throughout the duration of the
experiment. Transfers to 0 ppt, however, significantly decreased plasma osmolality
to 310 7.53 mOsm kg
(n¼7) by 6 h post-transfer, followed by a further
decrease to 269 12.75 mOsm kg
(n¼7) at 24 h. By 48 h, values increased to
271 11.46 mOsm kg
(n¼6), and were no longer different from the controls at
192 h, with a value of 359 13.73 mOsm kg
(n¼6). In contrast, transfer to 60 ppt
significantly increased plasma osmolality to 445 13.39 mOsm kg
(n¼6) at 24 h
post-transfer, with a further increase to 475 5.45 mOsm kg
(n¼6) at 48 h. Mean
osmolality had decreased by 96 h to 436 10.09 mOsm kg
(n¼6), and was no
longer different from the control at 192 h (439 7.71 mOsm kg
;n¼5), despite
water osmolality being around 1850 mOsm kg
(Table 1). Finally, fish transferred to
70 ppt significantly increased plasma osmolality to 437 15.64 mOsm kg
(n¼6) at
6 h post-transfer, a value that increased to 561 41.29 mOsm kg
(n¼6) by 24 h,
and resulted in death for all fish before 48 h. Overall, for all six salinity treatments,
backwards stepwise regression analysis suggested that plasma osmolality was only
related to salinity treatment, was unrelated to fish size and that there was no salinity
treatment by size interaction effect.
Mean hematocrit measurements (Figure 2) ranged from 31% to 43% for fish
transferred to salinities from 0 to 60 ppt, consistent with normal ranges observed in
many other species (32–43%). In control fish (30 ppt), hematocrit was maintained at
35 1.32% (n¼35). In transfers to 5, 50 or 60 ppt, blood hematocrit was maintained
Figure 2. Changes in blood hematocrit for the gray snapper L. griseus following abrupt
transfer to different experimental salinities. All fish exposed to 70 ppt died within 24–48h post-
transfer. Asterisks correspond to significant statistical differences with respect to controls
(P50.05; analysis of variance and Dunnet’s post hoc comparison test).
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at levels very similar to controls throughout the duration of the experiment, and no
significant differences among treatments were observed. Although transfers to 0 ppt
significantly increased blood hematocrit to 43 4.1% (n¼7) at 6 h post-transfer,
values had returned to control levels by 24 h (41 1.53%; n¼7). The opposite
occurred upon transfer to 70 ppt – a significantly reduced blood hematocrit
(274.5%; n¼6) was observed at 6 h post-transfer. However, by 24 h post-transfer,
hematocrit levels had returned to control levels (35 1.16%; n¼6) even though all
fish died. Because post-mortem blood sampling was not possible hematocrit values
after 24 h are unknown.
Field collections
Overall, fish collected in low salinity habitats (0–4 ppt) displayed a high variability in
plasma osmolality values, but these values were not significantly different from those
observed in the laboratory after transfer to freshwater (Figure 3). On the other hand,
fish collected in marine habitats displayed low variability in plasma osmolality values
that were significantly higher than those observed in the laboratory controls.
Abrupt transfers
This study investigated the osmoregulatory responses in plasma osmolality and
blood hematocrit displayed by the gray snapper after abrupt changes in ambient
salinity. Fish were challenged with six different salinity treatments including a
)tpp 03~( retawaeS)tpp 4-0( ytinilas woL
Plasma osmolality (mOsmKg
Lab Field
(26) (11) (35) (42)
)tpp 03~( retawaeS)tpp 4-0( ytinilas woL
Plasma osmolality (mOsmKg
Lab Field
(26) (11) (35) (42)
(26) (11) (35) (42)
Figure 3. Comparison of plasma osmolalities from gray snapper L. griseus in the
laboratory after transfer to either low salinity (0 ppt) or seawater (30 ppt, control) with gray
snapper after capture in the field at low salinities (0–4 ppt) and full-strength seawater
(30 ppt). Asterisks correspond to significant statistical differences between field and
laboratory results within each salinity ( P50.05; analysis of variance and Dunnet’s post hoc
comparison test).
Marine and Freshwater Behaviour and Physiology 191
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control (0, 5, 30, 50, 60, and 70 ppt) and blood samples were collected at various time
points post-transfer. Overall, results indicated no significant osmoregulatory
disturbances in the salinity range of 5–50 ppt. In contrast, at extreme salinities of
0 and 60 ppt, significant but transient changes in osmolality and/or hematocrit were
observed. However, by the end of the 192 h experimental period, both parameters
showed no significant differences with respect to control values, suggesting a
successful adaptation to these new salinity levels despite the large changes in
environmental salinity. Finally, the lethal salinity, defined by the concentrations
where a constant osmolality cannot be maintained (Foss et al. 2001), was observed at
70 ppt. However, the ability of the gray snapper to recover hematocrit to control
values within 24 h post-transfer to 70 ppt, even preceding 100% mortality, suggests
that fish were able to regain water balance even when they were unable to recover
salt balance.
From the few studies that have examined the effect of body size in euryhalinity,
the effect appears to be species-dependent. For example, after transfers from
seawater to both hypo- and hyper-saline media, Ferraris et al. (1988) found that
smaller milkfish Chanos chanos, not only had longer recovery times, but larger
deviations from control osmolality than larger fish (260 g) compared to milkfish (120
and 40 g). In contrast, Jensen et al. (1998) found no difference in parameters
observed during salinity acclimation when comparing large versus small European
sea bass Dicentrarchus labrax (89 g compared to 6.2 g sea bass), suggesting that this
species is euryhaline at all developmental stages. In this study, the range of sizes of
gray snapper tested varied greatly in every treatment (mean length in each ranged
from 14.1 to 23 cm TL, thus comprising both sub-adults and adults), but results
indicated no significant relationships between size and osmolality of fish tested in
any of the salinity treatments. Overall, these findings contradict previous field-based
observations (i.e. Starck 1964; Starck and Schroeder 1970), and suggest that larger
size classes of gray snapper may be equipped with the same efficient osmoregulatory
capabilities that juveniles possess. Thus, based on the results from this study, we
contend that gray snapper is a truly euryhaline species.
There is a paucity of literature on the immediate osmoregulatory responses for a
single species when abruptly transferred from seawater to both hypo- and hyper-
saline experimental media. Such information is available for more commonly studied
species including the European sea bass (Jensen et al. 1998; Varsamos et al. 2002),
red drum Sciaenops ocellatus (Crocker et al. 1983; Wakeman and Wohlschlag 1983),
milkfish (Ferraris et al. 1988) and Gulf toadfish Opsanus beta (Serafy et al. 1997;
Genz et al. 2008), among others. From these studies, it appears that the salinity range
to which gray snapper was able to acclimate during this study exceeded
corresponding ranges for the species listed above, particularly at the lower end of
salinity. For example, the Gulf toadfish, which is an important component of gray
snapper diet (Starck and Schroeder 1970), can successfully acclimate to hyperosmotic
salinities of up to 60 ppt with a slightly faster recovery time than the gray snapper
(596 h; Genz et al. 2008), but cannot survive in salinities of or lower than 0.5 ppt for
more than a week even after gradual acclimation (McDonald and Grosell 2006).
Similarly, the European sea bass can osmoregulate well over the same wide range of
salinities used in this study (0 to 60 ppt; Jensen et al. 1998). However, the few deaths
recorded in the initial adjustive phase of sea bass after transfer to freshwater also
suggest that the lower salinity threshold may fall between 5 and 0 ppt; contrasting
with the ability of gray snapper to osmoregulate well in freshwater.
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Field collections
To the best of our knowledge, this is the first study to compare measured plasma
osmolalities directly from fish captured in the field with laboratory-measured
osmoregulatory data. Overall, results showed that all size classes of gray snapper
captured within the same salinity in the field (15.5–31 cm TL in freshwater
collections, 9–30 cm TL in marine collections, respectively) displayed similar
osmoregulatory profiles. In addition, fish collected in low salinity habitats (salinities
ranging from 0–4 ppt) displayed osmolalities not significantly different from fish in
the laboratory transferred to freshwater. The high variability in the osmolalities
displayed in field-captured fish at these low salinities likely reflect differences in the
time that each fish had spent at the salinity of capture (i.e. indicative of migration
among habitats). In contrast, field-collected fish in full-strength seawater not only
displayed a smaller variability in osmolality values (consistent with the fact that these
areas tend to have stable salinities), but also unexpectedly displayed significantly
higher osmolality values compared to those in the laboratory at similar salinities.
These unexpected results may be explained by feeding differences in field versus
laboratory fish. While in the laboratory fish were fed solely with shrimp, in the field,
fish is the most prominent dietary component, particularly in larger size classes
(Starck and Schroeder 1970). Supporting this idea, Taylor and Grosell (2006) found
that a large meal of fish fed to the Gulf toadfish provided a substantial K
and Ca
load that significantly increased the osmolality measured when compared to a squid-
based diet. Alternatively, these higher than expected osmolality values in field-
captured fish at high salinities could have resulted from capture and/or handling
stress, albeit unmeasured. Further, osmolality has been shown to be affected by
handling and/or transporting stress (Redding and Schreck 1983; Denson et al. 2003),
which may explain why most osmoregulatory studies have an acclimation period
after fish capture and/or rearing. Whichever the case, it is important to emphasize
that field-measured osmoregulatory data are only suggestive of the conditions under
which this species is found in nature.
Ecological implications
In South Florida, alteration of freshwater flow has changed the salinity regimes and
degraded estuarine and nearshore habitats occupied by the gray snapper (Serafy
et al. 1997). Further, salinity is expected to undergo more significant changes with
the implementation of the Florida Everglades restoration, which aims at restoring
more natural, mesohaline salinity regimes within many of the South Florida’s coastal
bays (Walters et al. 1992; Harwell et al. 1996; Serafy et al. 1997). Gray snapper and
other species that are subjected to pulses of freshwater flow can either remain in these
areas, if physiologically capable, or leave and risk predation and/or food scarcity
while seeking a more benign habitat (Serafy et al. 1997). This study suggests that
even though freshwater pulses may represent a significant osmoregulatory challenge
to the gray snapper, this in itself will not lead to death. Gray snapper faced with a
freshwater pulse in their natural habitat are capable of remaining in such an area,
although their preferred food items may not. Early observations that multiple blood
drawings from the same individuals resulted in high mortalities (especially at
salinities of 0 and 60 ppt) suggest that while this species is highly tolerant of salinity
changes, when combined with other stressors (e.g. capture on hook-and-line), lesser
Marine and Freshwater Behaviour and Physiology 193
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salinity challenges than those tested may be lethal. Thus, research on the effects of
multiple stressors on the osmoregulatory capabilities of this species is warranted.
This work was conducted under Special Activity License no. 07SR-1015 (Florida Fish and
Wildlife Conservation Commission) and UM Institutional Animal Care and Use (IACUC)
protocol No. 07-017 (2007–2009). Financial support was provided through a fellowship from
NOAA’s Living Marine Resources Cooperative Science Center, the Cooperative Unit for
Fisheries and Education Research, RECOVER (US Army Corps of Engineers and South
Florida Water Management District) funds awarded to J. Serafy and NSF (IAB 0714024 and
0743903) funds awarded to M. Grosell. We are indebted to the technical support provided in
the lab and field by B. Teare, N. Hammerschlag (South Florida Student Shark Program),
D. Snodgrass, J. Stieglitz, the Audubon of Florida and members of the Grosell laboratory at
the University of Miami. D. Die and J. Lorenz contributed substantial guidance and supplies
facilitating this research.
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... = 10, P < 0·05). Serrano et al. (2011) tested sub-adult Gray Snapper osmoregulatory responses in the lab using plasma osmolality and blood hematocrit. They exposed fish to six salinity treatments including a control (0, 5, 30, 50, 60, and 70 ppt) and measured blood samples at various time points post-transfer. ...
... However, abrupt transfers of fish to a salinity of 70 produced 100% mortality within 48 h. Serrano et al. (2011) then compared their lab results to field measurements for fish captured in low salinity (0-4 PSU) versus marine (~ 30 PSU) habitats, and results suggested that osmoregulatory processes occurred similarly in both settings. There were no significant differences between size and osmolality of fish in any of their salinity treatments; therefore, the findings contradicted previous field-based observations (Starck 1964;Starck and Schroeder 1970), suggesting that larger Gray Snapper may be equipped with the same efficient osmoregulatory capability as juveniles. ...
... Salinity Fluctuations: As a species that spends much of its life in inshore habitats, including seagrass beds and mangroves, Gray Snapper may be subjected to wide salinity fluctuations brought on by water management actions, particularly in Florida (Serafy et al. 1997). Alteration of freshwater flows has changed the salinity regimes and degraded estuarine and nearshore habitats (Serafy et al. 1997), but the results of Serrano et al. (2011) indicates that although freshwater pulses represent a significant osmoregulatory challenge to Gray Snapper, the wide tolerances shown by that species should enable it to survive. However, Serrano et al. (2011) urged that, while this fish is highly tolerant of salinity fluctuations, additional research is needed to understand the combined effects of multiple stressors on its osmoregulatory capabilities. ...
Technical Report
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To supplement information needed to support Essential Fish Habitat (EFH) and the Fisheries Ecosystem Plan (FEP), the SAFMC contracted the Florida Fish and Wildlife Research Institute (FWC-FWRI) in 2012 to create a database called Ecospecies ( Major components of the Gray Snapper (Lutjanus griseus) species life history (SLH) include the following: Taxonomy, Geographic Range, Benthic Habitat, Water Column Habitat, Artificial Reefs, Shrimp Trawl Bycatch, Food Habits, Reproduction, Growth, Value and Status, Stock Enhancement, Population, Management Regulations, Ecological Interactions, and Human Impacts. Citations and references are available for each entry in the Ecospecies database. Almost everything published concerning this species is reviewed in the present SLH profile.
... laboratory settings and altered environmental levels) depends on the environmental variable in question and the rate and magnitude of change and the study species, but this process may take several weeks (e.g. Sidell et al., 1973;Morgan and Iwama 1998;Bouchard and Guderley, 2003;Serrano et al., 2011). Of the shuttlebox studies we surveyed, only 59% provided information on acclimation time prior to shuttle-box experiments. ...
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Animals' selection of environments within a preferred range is key to understanding their habitat selection, tolerance to stressors and responses to environmental change. For aquatic animals, preferred environmental ranges can be studied in so-called shuttle-boxes, where an animal can choose its ambient environment by shuttling between separate choice chambers with differences in an environmental variable. Over time, researchers have refined the shuttle-box technology and applied them in many different research contexts, and we here review the use of shuttle-boxes as a research tool with aquatic animals over the past 50 years. Most studies on the methodology have been published in the latest decade, probably due to an increasing research interest in the effects of environmental change, which underlines the current popularity of the system. The shuttle-box has been applied to a wide range of research topics with regards to preferred ranges of temperature, CO 2 , salinity and O 2 in a vast diversity of species, showing broad applicability for the system. We have synthesized the current state-of-the-art of the methodology and provided best practice guidelines with regards to setup, data analyses, experimental design and study reporting. We have also identified a series of knowledge gaps, which can and should be addressed in future studies. We conclude with highlighting directions for research using shuttle-boxes within evolutionary biology and behavioural and physiological ecology.
... A las especies que tiene la capacidad de sobrevivir dentro de ciertos intervalos de salinidades se les denomina eurihalinas y estas pueden ser de dos tipos, las que toleran y se adaptan a fluctuaciones rápidas de la salinidad externa y las que realizan migraciones en algún momento de su ciclo vital entre medios dulceacuícolas y marinos (Nordlie y Haney 1998). Gran parte del trabajo sobre las respuestas osmorreguladoras se ha realizado principalmente en salmónidos (Serrano et al. 2011). Basado en lo anterior, en este trabajo se evaluó la tolerancia fisiológica al cambio de salinidad, bajo condiciones de laboratorio, de D. latifrons, con el objetivo de aportar conocimiento sobre la capacidad de osmorregulación bajo condiciones controladas, y establecer las condiciones ambientales en las que puede ser mantenida en cultivo. ...
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Dormitator latifrons inhabits a wide range of salinities as a result of its migratory and reproductive cycle. The objective of the study was to evaluate the physiological response time and survival to saline change under laboratory conditions. The basal gill ventilation frequency (GVF) of organisms was recorded at 33 ups (SW) and in freshwater at 0.3 ups (FW). The gill ventilation frequency of organisms that were transferred from FW-SW and inversely from SW-FW (15, 25, and 33 ups) was counted, in triplicate, for 1 minute and 1, 4, 24 and 48 h. Statistical differences (p < 0.05) were found in fish transferred from FW-SW and SW-FW at the first minute with respect to basal GVF. In all treatments the organisms recovered their GVF one hour after being exposed to saline modification. There was 100% survival in all treatments. D. latifrons has a rapid physiological response to sudden changes in salinity.
... Osmoregulation has been widely studied in marine organisms (e.g. Deaton, 1981;Evans, 1981;Sang & Fotedar, 2004;Serrano et al., 2011;Torres et al., 2011), where the vast majority of taxa are osmoconformers (Willmer et al., 2005;). In contrast, our knowledge of the osmotic mechanisms of organisms inhabiting inland waters is severely limited, despite the fact that information on the salinity tolerance of such taxa is essential for understanding their ecology and evolutionary history (e.g. ...
... Functional changes are reflected in the differentially expression of the various genes in the kidney. However, only few studies have examined the physiological response of the teleost kidney to abrupt salinity changes, especially within 6 h of the change, because of a lack of a suitable model (Herrera et al., 2012; Xaymara et al., 2011). One study using spotted scats studied the osmoregulation of the kidney, but the earliest time point examined was at 1 day after the transfer from saltwater to freshwater and focused primarily on morphological changes (Chenari et al., 2011). ...
The spotted scat (Scatophagus argus) is a euryhaline marine fish with the capability to withstand different salinity levels and can tolerate abrupt transfer from salt water (SW) to fresh water (FW) or vice versa. Differentially expressed genes were identified by constructing suppression subtractive hybridization (SSH) cDNA libraries to explore branchial osmoregulatory mechanisms affected by salinity challenge. After trimming and blasting, 105 uniquely expressed sequence tags were identified. Among them, 24 candidate genes involved in the stress response, metabolism, and the respiratory chain were chosen for further validation by real-time polymerase chain reaction. More than two-fold expression differences were observed in ADP-ribosylation factor 1 (arf1), cyclic AMP-responsive element-binding protein 3-like 4 (creb3l4), EVI5-like protein (evi5l), protocadherin fat 2 (fat2), transferrin receptor protein 2 (tfr2), C-X-C chemokine receptor type 4 (cxcr4), aquaporin-3 (aqp3), sodium/potassium-transporting ATPase subunit beta-233 (nka β233), serum and glucocorticoid-regulated kinase 1 (sgk1), and ras GTPase-activating-like protein IQGAP1 (iqgap1). Among these genes, aqp and nka are important osmoregulatory factors. AQP3 protein was observed being localized to the membranes of mitochondrion-rich cells (MRCs) and pillar cells of the gill of S. argus, and NKA β233 subunit isoform was only found in MRC membranes by immunostaining. Significant differences in aqp3 and nka β233 expression occurred within 24 h after being transferring into the freshwater, and nka β233 expression level continued to highly upregulated 2 and 7 days post-transfer (dpt). These results suggest that branchial aqp3 and nka β233 play important roles in response to hypo-osmotic stress in S. argus.
... The initial decrease in plasma osmolality within 3 h of transfer to TW suggested that there is a continuous loss of ions and that fish is not able to immediately reactivate its salt uptake mechanism in TW. Other reports also show decrease in plasma osmolality of fishes with the decrease in external salinity (Evans, 1980; Mancera et al., 1993; Prodocimo et al., 2008; Sangiao-Alvarellos et al., 2003 Sayer and Reader, 1996; Serrano, et al., 2011;Woo and Fung, 1981). The results also reveal a significant elevation of plasma glucose within 3 h of transfer of the catfish both in 30% and 35% SW and are in accordance with earlier findings (Arjona et al., 2007; Assem and Hanke, 1979; Fiess et al., 2007; Hegab and Hanke, 1984; Krayushkina, 1998; Parwez et al., 2001b; Sangio-Alvarellos et al., 2003). ...
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Biological aspects of the terrestrial yellow garden slug (Tawny Garden Slug) Limax flavus (Linnaeus) including ovipostion, hatching, generation period, life span as well as growth parameters were studied under laboratory conditions. Results revealed that mating is not essential for this species to lay eggs, while self-fertilization is the normal breeding system. The oviposition period averaged 62.4 ± 30.9 days, during which the individual laid an averaged of 41.1 ± 20.4 eggs. The incubation period averaged 21.0 ± 2,4 days, while the generation period (from egg to egg) lasted 152,8 ± 18.8 days in average. On the other hand, the maximum life span durated an average of 235.2 ± 27.5 days. Growth parameters, depending on the increase and decrease of the slug body weights, increased from hatching until the seventh month and reached its maximum weight averaging 3.51 ± 0.86 g. The maximum change rate in weight was in the first month reached to 78.8 ± 17.2 %. The change rate in weight decreased thereafter due to the climatic conditions.
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Context: The Navío Quebrao lagoon (NQL) has always played an important role in the economy of the indigenous communities in its surroundings. However, in recent years, the tributaries to the lagoon have been notably impacted by climatic variability and logging activities, therefore clogging the lagoon and causing the loss of depth, which increases the temperature and salinity. In three months, 80% of the lagoon dries out, causing the mortality of most of the species inhabiting it. This phenomenon is known as the Cachirra event. Therefore, this study aims to analyze the incidence of environmental, biological, amd fishing factors in the formation and mortality of the Cachirra event.. Methodology: We collected samples from fishing nets used by the fishermen of the arranchaderos community. IDEAM provided 2017 climatologic data. Physicochemical variables were measured with a Spectroquant SQ 118 and other direct measurement electronic devices. The R statistical software version 3.2.2 was used to analyze the data and their relationships. Results: The results showed that 12 species are involved in the formation of the Cachirra event, predominantly the Mugilidae family. Salinity was the physicochemical variable that predominantly affected the mortality of the species -October (6,0 ± 0,6 UPS) and March (67,4 ± 1,36 UPS). Conclusions: Fish die according to their susceptibility to salinity changes, with Cathrorops spixii and Eugerres plumieri being the most susceptible species and Elops saurus and Mugil liza the most resistant. The species present in the NQL have lengths well below commercial significance and different condition factor and repletion index values before and after the Cachirra event. Funding: Universidad de La Guajira
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Snappers are marine fishes, but juveniles of many species migrate to estuaries, using these systems as nursery areas. The purpose of this study was to know the environmental factors mainly related to the migration patterns of lutjanids in La Mancha lagoon inlet. During 19 months, 24-hour cycles were performed monthly, taking samples every two hours (442 samples). Environmental variables recorded in situ and with regional records such as rainfall, atmospheric temperature and day length were considered. Genetic barcoding (COI) was used to validate species identity. Significant differences were evaluated by PERMANOVA and a Canonical Correspondence Analysis was used to determine the importance of environmental variables. Six species were recorded and the most abundant showed significant differences among months, with migration patterns during the warm-rainy season. Day length, salinity and rainfall (two of them with regional incidence) were the variables significantly associated with the distribution of the species. The abundance of Lutjanus analis, L. jocu, and L. cyanopterus was inversely associated with the length of daylight and directly related to rainfall, while L. synagris and L. griseus showed segregation along a salinity gradient. Thus, migration patterns were mainly correlated with factors of regional coverage and greater seasonal influence.
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In Latin America snapper species have shown great potential for mariculture, including L. guttatus, but it is necessary to study physiological aspects regarding its production. The purpose of this study was to determine the effects of temperature (24, 29 and 34 degrees C) and salinity (15, 25, 35, 45) on the growth and survival of juvenile L. guttatus. All experiments were performed in a recirculation system with daily 300% change of water; in cylindrical 80 L tanks, and three replicates per treatment. 360 specimens were used for the experiments. Experiments were performed with 360 specimens. The results showed that there are differences (P < 0.05) in salinity-temperature interaction. The highest specific growth rate appeared in the treatment of 34 degrees C and salinity of 15. The greatest gain in average body weight was obtained in the treatment of 34 degrees C and salinity of 25. The longer survival was recorded in the treatment of 24 degrees C and salinities of 15 to 35. The low salinity tolerance for this species found shows that L. guttatus has a high potential to grow in lagoon-estuarine systems of low salinity (15) and no more than 35.
NaCl-rich rock salt dissolved in natural water source leads to salinity fluctuation that profoundly affects freshwater ecosystem and aquatic fauna. The snakehead (Channa striata) can live in saline water, but the osmoregulatory mechanisms underlying this ability remain unclear. Herein, we found that exposure to salinities ≥10 ‰ NaCl markedly elevated plasma cortisol and glucose levels, and caused muscle dehydration. In a study of time-dependent response after being transferred from fresh water (0 ‰ NaCl, FW) to salt-dissolved brackish water (10 ‰ NaCl, SW), FW-SW, cortisol increased rapidly along with elevations of plasma glucose and lactate. Interestingly, plasma cortisol returned to baseline after prolonged exposure, followed by a second peak that probably enhanced the branchial Na(+)/K(+)-ATPase activity. Under SW-FW condition, Na(+)/K(+)-ATPase activity was not altered as compared to SW-adapted fish. In conclusion, salinity change, especially FW-SW, induced a stress response and hence cortisol release in C. striata, which might increase plasma glucose and lactate to energize the branchial Na(+)/K(+)-ATPase.
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Newly recruited juvenile gray snapper Lutjanus griseus were collected each fall for two consecutive years (2000 and 2001) from sites in Florida and North Carolina. Spawning, settlement, and growth patterns were compared across sites based on otolith microstructure. Larval otolith growth trajectories were generally similar for larvae from different sites and years; however, the mean pelagic larval duration (PLD) was 1 d longer for fish from North Carolina than for fish from the more southern sites. As a result, fish were larger at settlement to North Carolina. Estimated juvenile growth rates ranged between 0.62 and 0.88 mm/d and differed across sites and years, growth being generally faster at the southern sites. Water temperature accounts for some of this variability; however, site-specific differences in other factors probably contributed to some of the observed differences in growth. Back-calculated spawning patterns showed a lunar association with the new and first-quarter moons at all sites except for North Carolina. Settlement patterns were lunar cyclic as well: settlement pulsed during the third-quarter and new moons at all sites, and in North Carolina an additional pulse associated with the full moon was present. Patterns of larval and juvenile growth coupled with recruitment dynamics across the latitudinal gradient are consistent with northward Gulf Stream transport of larvae from southern spawning sites.
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A 14 mo trawl survey was conducted at 8 study sites in Biscayne Bay, Florida, USA, to compare the species composition and structure of juvenile fish assemblages found near the mouths of freshwater flood control canals with those in similar areas with relatively stable salinity regimes. Water temperature, salinity, dissolved oxygen and depth measurements were recorded during fish sampling and bottom vegetation was also quantified. The survey yielded a total of 38134 individuals from 95 taxa. Fish species composition was similar among sites, but more species were collected from stable-versus variable-salinity areas. Mean fish abundance and the mean abundances of Eucinostomus gula, Lagodon rhomboides, Opsanus beta and Lutjanus griseus shared a general pattern of increase from north to south, with highest values occurring at one or more of the canal-influenced sites. In contrast, mean species richness and the mean abundances of Lucania parva, Haemulon sciurus, H. plumieri, and H. parra were significantly greater at stable-salinity sites than at variable-salinity sites. Freshwater challenge experiments were then conducted on each of the fishes above, as well as on 2 relatively uncommon species, Cynoscion nebulosus and Cyprinodon variegatus. The mortality of groups exposed to a single, rapid, freshwater pulse (i.e. salinity was changed from approximately 32 ppt to 0 to 32 ppt over 2 h) was compared with that of controls. Of the 8 fishes that dominated the nearshore habitats of Biscayne Bay, 5 exhibited no mortality and L. rhomboides, L. parva, and H. plumieri exhibited 12.5, 50 and 100% mortality rates, respectively. Mortality was 100% for the relatively uncommon C. nebulosus and C. variegatus. Results suggest that the differential osmoregulatory abilities of the species tested may underlie some, but not all, of the structural differences observed between fish assemblages from stable-salinity habitats versus those adjacent to freshwater canals.
Documented interest in the fishery resources of Florida Bay dates from the earliest accounts of human activity. However, prior to the 1940's, fishing activities were largely subsistence oriented, providing only supplemental family income. The first large-scale directed fishery was for striped mullet. Increased development of south Florida, improved transportation, and population growth all led to increased sport fishing activities during the 1940's and 1950's. By the early 1970's, there were an estimated 25 000 recreational fishing trips a year to Florida Bay. Commercial activities reached a peak between 1977 and 1978 when over 350 individuals held permits to guide or fish commercially using nets, hook-and-line, or traps. Concern for the conservation of Florida Bay's marine resources quickly followed the explosion of commercial and recreational use occurring in the late 1940's. Florida Bay was added to Everglades National Park in 1950 and, in 1951, the first special government regulations were established to control the methods, species, and locations of fish harvest, although no systematic effort was made to collect accurate catch and harvest statistics until 1958. The National Park Service (NPS) monitoring program has provided detailed data on the fishing effort and harvest of both commercial and recreational fisheries up to the present time. The total recreational fish harvest from Florida Bay by guided and non-guided parties has ranged between 700 000 and 800 000 fish per year since 1984. Species most frequently sought by guide fishermen include tarpon, bonefish, snook, spotted seatrout, gray snapper, red drum, and Spanish mackerel. -from Author
Marshland drainage and water regulation have greatly altered the Florida Everglades. One of the most visible ecological impacts has been a drastic decline in nesting populations of wading birds, and several specific hypotheses have been advanced to explain the decline. Recent efforts at ecological restoration have concentrated on reestablishing more natural seasonal hydropatterns in freshwater marsh areas now used extensively by the wading birds. However, nesting colonies were originally concentrated along the estuarine mangrove edge of the system rather than around upstream marshes. Hydrological simulation models have been used to reconstruct what hydrological conditions might have been like in the natural system, and these simulations indicate that freshwater pools near and flows to the estuary have been drastically reduced, especially late in the annual spring drying season. An experimental program of increased water releases to the estuary could be used to test whether estuarine restoration is a necessary condition for recovery of wading bird populations. This program would require a substantial commitment to deliver runoff from the Everglades Agricultural Area into the marshes, and to minimize water diversions for flood control and well field recharge
Yearling coho salmon Oncorhynchus kisutch acclimated to fresh water or seawater were subjected to severe chronic confinement stress in fresh water, seawater, or a medium (one-third-strength seawater) that was approximately isosmotic to the fish's blood. Plasma osmolarity, Na, K, Ca, Mg, and cortisol and blood hematocrit were measured in fish sampled at 1, 7, 24, and 48 hours after stress began. Plasma osmolarity and electrolyte concentrations increased during stress in seawater, but generally decreased during stress in fresh water. Osmotic imbalance did not occur in fish that were stressed in one-third seawater. Hematocrit increased in fish stressed in fresh water and decreased in fish stressed in seawater. Fish acclimated to fresh water tended to regain osmotic balance within 48 hours when stressed in fresh water, but in seawater they died. Fish acclimated to seawater tended to regain osmotic balance within 48 hours when stressed in seawater, but in fresh water a compensatory trend was not evident. Confinement stress greatly amplified the osmotic imbalance after fish were transferred from fresh water to seawater compared with that in unconfined fish. Plasma cortisol concentrations increased during stress for all groups; however, fish stressed in one-third seawater had lower concentrations of cortisol than the other groups within 7 hours after stress began.Received February 8, 1983 Accepted August 7, 1983