Tarpons: Biology, Ecology, Fisheries

Table of Contents

Cover

Title Page

Preface

Acknowledgements

Symbols and abbreviations

CHAPTER 1: Development

1.1 Introduction

1.2 The tarpon leptocephalus

1.3 Staging tarpon ontogeny

1.4 Development of Atlantic tarpons

1.5 Development of Pacific tarpons

1.6 Leptocephalus physiology

CHAPTER 2: Growth

2.1 Introduction

2.2 The cube law

2.3 Sexually dimorphic growth

2.4 Condition

2.5 Growth rate

2.6 Modeling growth

2.7 Tarpon larvae

CHAPTER 3: Spawning

3.1 Introduction

3.2 Fecundity and early survival

3.3 Where tarpons spawn

3.4 When tarpons spawn

3.5 Size and age at maturity – Atlantic tarpons

3.6 Size and age at maturity – Pacific tarpons

CHAPTER 4: Recruitment

4.1 Introduction

4.2 Life in the plankton

4.3 Inshore migration

4.4 Offshore migration

4.5 Mechanisms of recruitment

4.6 Factors affecting recruitment

CHAPTER 5: Breathing and respiration

5.1 Introduction

5.2 Water-breathing

5.3 Air-breathing

5.4 Cardiovascular function

5.5 Hypoxia

5.6 Hypercapnia

5.7 Air-breathing as social behavior

CHAPTER 6: Osmo- and ionoregulation

6.1 Introduction

6.2 Osmo- and ionoregulation

6.3 Ionocytes

6.4 Acid-base regulation

6.5 Ammonia excretion

6.6 Euryhaline transition

6.7 Endocrine factors

6.8 Eggs and larvae

CHAPTER 7: Ecology

7.1 Introduction

7.2 Habitats

7.3 Predators of tarpons

7.4 Environmental factors affecting survival

7.5 Gregariousness

7.6 Seasonal movements

7.7 Feeding and foods

CHAPTER 8: Fisheries

8.1 Introduction

8.2 Recreational fisheries

8.3 Handling

8.4 Stress effects

8.5 Commercial fisheries

8.6 Aquaculture

8.7 Populations

8.8 Final note: whom should we save?

APPENDIX A: Partial list of countries where Atlantic and Pacific tarpons have been reported

Atlantic tarpons

Pacific tarpons

APPENDIX B: Contribución a la morfología y organogenésis de los leptocéfalos del sábalo Megalops atlanticus (Pisces: Megalopidae)

Stage I (Leptocephalic Growth)

Stage II (Shrinking Leptocephalus)

Stage III (Juvenile Growth)

APPENDIX C: Desarrollo temprano del sábalo, Megalops atlanticus (Pisces: Megalopidae)Early development of the tarpon, Megalops atlanticus (Pisces: Megalopidae)

Material and methods

Results and discussion

APPENDIX D: Aspectos biométricos de una población de sábalo, Megalops atlanticus (Pisces: Megalopidae)Biometric aspects of a tarpon population, Megalops atlanticus (Pisces: Megalopidae)

Material and methods

Results and discussion

APPENDIX E

Partial list of food items consumed by Atlantic tarpons

Partial list of food items consumed by Pacific tarpons

APPENDIX F: Sôbre a alimentação do camurupim, Tarpon atlanticus (Valenciennes), no Estado do CearáOn food of the tarpon, Tarpon atlanticus (Valenciennes), in the State of Ceará

Material and method

Discussion and conclusions

APPENDIX G: Ecología básica y alimentación del sábalo Megalops atlanticus (Pisces: Megalopidae)

Results and discussion

APPENDIX H: Ensaio preliminary sobre o cultivo camurupim (megalops [sic] atlanticus) em viveiros escavados e sua ocorrência em lagoas marginais no litoral de Tutóia – Ma

APPENDIX I: Sobre a elaboração de conservas de pescado em leite de côco em óleos de algodão e de babaçu

Material and methods

Results and discussion

Conclusions

APPENDIX J: Industrialização da ova do camurupim, Tarpon atlanticus (Valenciennes)

Material and methods

Conclusions and recommendations

Summary

References

Index

End User License Agreement

List of Tables

Preface

Table 0.1 Length-length, length-weight, and otolith weight-age regressions for Atlantic tarpons from south Florida waters. Values of length in mm, weight (W) in kg, otolith weight (OW) in g, age in years (y). Length range for length-length regressions = 106–2045 mm FL; length range for length-weight regressions = 102–2045 mm FL; age range for OW weight-age regressions = 1–55 years (females) and 1–43 years (males).

Chapter 01

Table 1.1 Growth stages and phases partitioned by length of Atlantic tarpon leptocephali (Stages 1 and 2) and fry (Stage 3). Stage 3 has been modified to 13.0–45.0 mm SL based on Harrington’s (1958) finding that allometric growth ceases at ≈ 45 mm SL. See text for an explanation of phases.

Chapter 03

Table 3.1 Weight, standard length, and age at sexual maturity of female Atlantic tarpons in southern Florida. Sample size (n) in parentheses.

Table 3.2 Frequencies of Atlantic tarpon by length class, sex, and maturation status caught in commercial fisheries at Acaraú, Ceará, Brazil during 1962 to 1964. Total males and females combined = 2469.

Chapter 04

Table 4.1 Lengths and weights of Pacific tarpon leptocephali and juveniles from Tadu Creek (estuary and freshwater upper reaches) and adjacent offshore waters, western Taiwan. L = length, W = weight, = mean, ± SD = standard deviation, n = sample size.

Chapter 05

Table 5.1 Hematological values of sagors (Hexanematichthys leptaspis 280–570 mm FL) and Pacific tarpons (258–303 mm FL from a northern Australian billabong.

Chapter 07

Table 7.1 Assignment test of individual Atlantic tarpons to their 15 source populations. Collection site designations: United States – North Carolina (NC), Florida west coast (FL), Louisiana (LA), Texas at two locations designated upper and lower (TU, TL); México – Tampico (Ta), Tecolutla (Te) Veracruz (Ve), Chetumal (Ch); Costa Rica (CR); Panamá, Pacific coast (Pa); Puerto Rico (PR); Colombia, Caribbean coast (Co); Brazil, state unspecified (Br); Nigeria, western Africa (Af). Total n = 328.

Table 7.2 Assignment test of individual Atlantic tarpons to their 15 source populations. Collection site designations: United States – North Carolina (NC), Florida west coast (FL), Louisiana (LA), Texas at two locations designated upper and lower (TU, TL); México – Tampico (Ta), Tecolutla (Te) Veracruz (Ve), Chetumal (Ch); Costa Rica (CR); Panamá, Pacific coast (Pa); Puerto Rico (PR); Colombia, Caribbean coast (Co); Brazil, state unspecified (Br); Nigeria, western Africa (Af). Total n = 328.

Table 7.3 Prey-switching in Pacific tarpons according to body length (SL) during October–December 1963 in backwaters of the Cooum River, Chennai, India. Percentages are by volume.

List of Illustrations

Chapter 01

Fig. 1.1 Higher-level classification of orders in the Elopomorpha along with numbers of taxa presently included. Representative larval and adult body forms are illustrated for each group. The Elopiformes, to which the two extant species of tarpons (Megalops atlanticus and M. cyprinoides) belong, is represented by a ladyfish, of which six species exist (Elops spp.).

Fig. 1.2 A modern phylogenetic hypothesis about the monophyly of Elopomorpha. See source publication for history and details.

Fig. 1.3 (a) Atlantic tarpon fry, Stage 3 phase X (16.9 mm SL). (b) Atlantic tarpon in late Stage 3 (41.0 mm SL) approaching the end of allometric growth.

Fig. 1.4 Profiles of an Atlantic tarpon 36.8 mm SL (broken lines) and an earlier specimen of 16.0 mm SL (solid lines), the second superimposed onto the first and enlarged proportionately so that standard lengths of the two illustrations coincide.

Fig. 1.5 Illustration of an adult Pacific tarpon showing the elongated last ray of the dorsal fin.

Fig. 1.6 Stages 1 and 2 Atlantic tarpon larvae.

Fig. 1.7 Atlantic or Pacific tarpon larva, depicting where some (but not all) measurements are typically taken. Numbers indicate the following measurements (mm) or counts (9–15 not illustrated): 1 – standard length (SL); 2 – head length (HL) tip of snout to posterior fleshy margin of operculum; 3 – snout length, tip of snout to anterior edge of bony orbit; 4 – eye diameter, anterior inner edge of bony orbit to posterior inner edge of orbit; 5 – depth, angle of base of pelvic fin vertically to dorsal outline of body; 6 – prepelvic length, tip of snout to origin of pelvic fin; 7 – predorsal length, tip of snout to origin of dorsal fin (or dorsal fin fold); 8 – preanal length, tip of snout to origin of anal fin (or posterior edge of anus); 9 – fin-ray counts; 10 – total myomere counts, from anterior-most to last myomere in caudal area, these last becoming indistinct when hypural plate forms; 11 – prepelvic myomere counts, from anterior-most myomere to myomere the ventral extremity of which approximates origin of pelvic fin; 12 – predorsal and preanal myomere counts, same as 11 above; 13 – lateral line scales, counted from opercular flap to posterior scale of caudal fin; 14 – teeth, number on each side of upper and lower jaws; 15 – gill rakers, number (including rudiments) on upper and lower limbs of first gill arch on one side.

Fig. 1.8 Early Stage 1 Atlantic tarpons from the Yucatán Channel, Mexican Caribbean, and Gulf of Mexico (exact collection locations unclear). (a) 5.7 mm NL, (b) 6.3 mm NL, (c) 8.1 mm NL). Scale bars = 1 mm.

Fig. 1.9 (a) Pacific tarpon, (b) Atlantic tarpon. The distance in (a) represented by the line 3 is longer than that represented line 3 in (b). The position of the ventrals is farther form the tip of the snout in (a) than the (b). Lines 1 and 2 are equal in both, showing that position of the dorsal fins is identical in the two species.

Fig. 1.10 Tarpon scales. (a) Pacific tarpon of 300 mm SL, 15th scale in the lateral line from below the anterior margin of the dorsal fin (see Text-fig. 9 of source publication). (b) Atlantic tarpon of 238 mm SL, 18th scale in the lateral line from below the anterior margin of the dorsal fin (see Text-fig. 11 of source publication).

Fig. 1.11 First illustration of a Pacific tarpon leptocephalus (≈25 mm TL or ≈ 22 mm SL). The specimen is probably Stage 2 based on the presence of pelvic fins and pigment, dorsal and anal fins placed far back, and advanced development of median fins and swim bladder (Wade 1962: 594). The inshore capture site is also diagnostic.

Fig. 1.12 Sequence of squamation development in Pacific tarpons during the juvenile growth phase. (a) 22.4 mm SL. (b) 24.3 mm SL. (c) 26.2 mm SL. (d) 27.0 mm SL. (e) 30.0 mm SL. (f) 33.5 mm SL.

Fig. 1.13 Model postulating mechanisms of nutrient acquisition, Na+ and Cl- fluxes, and gas exchange in elopomorph Stage 1 leptocephali. The large, laterally-compressed body offers a high surface-to-volume ratio, favoring cutaneous respiration (the gills are not yet developed) and different pathways for possible uptake of dissolved organic matter (DOM). A portion of the Na+ and Cl– that enter passively by diffusion, including via Na+-DOM cotransport involving specific carrier proteins (filled circles), and by intestinal absorption (along with water and ingested DOM, is bound to acidic glycosaminoglycans (GAGs). Some NaCl is probably transported actively out of the body by means of ionocytes (I) in the integument (see Chapter 6.3). Water and NaCl of leptocephali increase as GAG concentrations in the extracellular gelatinous body matrix rise during Stage 1 growth. The integument is also an important site of ammonia (designated here as NH3) excretion.

Chapter 02

Fig. 2.1 Weight vs. length relationship for Stage 2 Atlantic tarpons from Indian River Lagoon, eastern Florida (range = 16.0–45.5 mm SL, n = 154). © American Society of Ichthyologists and Herpetologists.

Fig. 2.2 Scatter plot of mean log a (TL) over mean b for 1223 fish species with accompanying body shape information: clear circles, short and deep; plus signs, fusiform; short horizontal bars, elongated; long horizontal bars, eel-like. Areas of negative allometric, isometric, and positive allometric change in W vs. L are shown. Regression line is based on a robust analysis of fusiform species (n = 451): intercept = 2.322 – 0.133 = 2.189, slope as in log a = –1.358b + 2.322 – 1.137 (1 if eel-like, otherwise 0), –0.3377 (1 if elongated otherwise 0), –1331 (1 if fusiform otherwise 0).

Fig. 2.3 Change in B with length/girth ratio in salmons. Clear triangles, Atlantic salmons; clear squares, chinook salmons; x, smolts. See text for explanation of the B factor.

Fig. 2.4 Growth sequence over 50 days of Atlantic tarpons from inshore locations of Golfo de Morrosquillo, Colombian Caribbean. Scale bars in mm (0–3).

Fig. 2.5 Observed mean lengths (±2 SD) and predicted lengths from the von Bertalanffy growth model for male and female Atlantic tarpons.

Fig. 2.6 Von Bertalanffy growth curves for male (a) and female (b) Atlantic tarpons showing fork length plotted against estimated radiometric age and compared with annulus-derived age. Vertical bars represent FL range for age groups. Horizontal bars represent low and high radiometric age estimates.

Fig. 2.7 The smallest post-larval Atlantic tarpon recorded by Harrington (1958). It measured 16.0 mm SL (18.8 mm TL).

Chapter 03

Fig. 3.1 One of the two ovaries of a 100 kg (≈ 220-lb) female Atlantic tarpon.

Fig. 3.2 Partial survival curves for larvae of Adriatic Sea pilchards, Sardina pilchardus, (clear circles) and northern anchovies, Engraulis mordax (solid circles) as percentage total larvae vs. length (presumably TL). The association is negative, indicating decreasing percentage mortality with increasing length.

Fig. 3.3 Estimated hatching dates of Atlantic tarpon leptocephali caught at Sebastian Inlet, Indian River Lagoon Florida during summer 1994. Clear circles represent full moons.

Fig. 3.4 Lunar periodicity in hatching dates for 41 Atlantic tarpon leptocephali caught at Sebastian Inlet, Indian River Lagoon, Florida during summer 1994. Rayleigh’s test of circular distributions (Z = 11.71, n = 41, p < 0.001) indicates a non-uniform hatching distribution through the lunar months. Solid circle represents new moon, clear circle represents full moon.

Fig. 3.5 Length-frequency distributions of mature male and female Atlantic tarpons from southern Florida and Costa Rican waters.

Fig. 3.6 Double-Y scatter plots of length at sexual maturity of male Atlantic tarpons caught in coastal weirs at Acaraú, Ceará State, northeastern Brazil 1962–1964 (total n = 1186): solid squares are immature fish without sperm (n = 205), clear circles mature fish with sperm (n = 981). Length categories on the abscissa represent 27 range classes of length (FL in cm): 1 (55.0–59.5), 2 (60.0–64.5), 3 (65.0–69.5), 4 (70.0–74.5), 5 (75.0–79.5), 6 (80.0–84.5), 7 (85.0–89.5), 8 (90.0–94.5), 9 (95.0–99.5), 10 (100.0–104.5), 11 (105.0–109.5), 12 (110.0–114.5), 13 (115.0–119.6), 14 (120.0–124.5), 15 (125.0–129.5), 16 (130.0–134.5), 17 (135.0–139.5), 18 (140.0–144.5), 19 (145.0–149.5), 20 (150.0–154.5), 21 (155.0–159.5), 22 (160.0–164.5), 23 (165.0–169.5), 24 (170.0–174.5), 25 (175.0–179.5), 26 (180.0–184.5), 27 (185.0–189.5).

Fig. 3.7 Double-Y scatter plots of length at sexual maturity of female Atlantic tarpons caught in coastal weirs at Acaraú, Ceará State, northeastern Brazil 1962-1964 (total n = 1283): clear circles are fish with immature and maturing ovaries (n = 471), solid squares fish with mature and spent ovaries (n = 812). Length categories on the abscissa same as Fig. 3.5.

Fig. 3.8 Pacific tarpon, 300 mm SL.

Chapter 04

Fig. 4.1 Part of a coastal fish weir set at Acaraú, Ceará State, northeastern Brazil. Note the spaces between the vertical sticks, which appear wide enough to allow small Atlantic tarpons to escape.

Fig. 4.2 Daily catches of larval Atlantic tarpons at channel-net stations set at Sebastian Inlet, Indian River Lagoon, Florida in summer 1995 (total n = 723). Clear circles represent full moons.

Fig. 4.3 Lunar cycle of Atlantic tarpon leptocephali caught at Sebastian Inlet, Indian River Lagoon, Florida during summer 1995. Rayleigh’s test of circular distributions (Z = 8983.0, n = 723, p < 0.001) indicates non-uniform hatching through the lunar months. Solid circle represents a new moon, clear circle a full moon.

Chapter 05

Fig. 5.1 Oxygen cascade: the series of convective, diffusive, and biochemical barriers that progressively lower the partial pressure of oxygen until it reaches near-anoxic levels necessary for optimal mitochrondrial intracellular function.

Fig. 5.2 Diagrammatic structure of a teleost gill. Arrows indicate direction of water flow.

Fig. 5.3 Water-breathing (aquatic ventilation) by bony fishes. (a) Inspiration: the opercula close, the velar fold (oral valve) opens, the buccal cavity dilates with expansion of the gill arches, and water enters. (b) Expiration: the velar fold closes, the gill arches contract, the opercula open, and water is forced over the gill filaments and into the pharynx. Plus and minus signs indicate positive and negative pressure.

Fig. 5.4 (a) Swim bladder of a 1.3 kg Atlantic tarpon cut on the dorsal side and laid open to reveal its internal surface. The four ridges of respiratory tissue extend along the length of the swim bladder, and the ventral ridge and one lateral ridge (top) are interconnected in the organ’s anterior region. (b) Swim bladder of a 13.7 kg specimen laid open as in (a) showing little connection between respiratory ridges. The dorsal ridge (bottom) extends anterior of the pneumatic duct (PD) into the narrow tubular projection of the swim bladder under the skull. (c) Swim bladder of a 38.6 kg specimen laid open as in (a) and (b). Some vascular connections between respiratory ridges are present. (d) Magnified view of dashed box in (c) showing a large blood vessel connecting two ridges of respiratory tissue. (e) Enlarged image of the dashed box in (b) showing the faveolata surface of the ventral respiratory ridge. (f) SEM image of the dashed box in (e) revealing the interconnected septa forming air chambers of different sizes. (g) Magnified view of the dashed box in (f) showing the respiratory surface of the interconnected septa. (h) Enlarged view of box in (g) showing the respiratory epithelium.

Fig. 5.5 Light and scanning electron microscope (SEM) images of transverse sections through the swim bladder respiratory tissue of a 13.7 kg Atlantic tarpon. (a) The main conduit artery and vein extend along the base of each ridge of respiratory tissue and appear to distribute and collect blood along its length. A segmental artery leaves the main conduit artery to deliver blood to the respiratory septa. (b) Magnified image of dashed box in (a), showing the interconnected respiratory septa and associated air spaces. (c) Enlarged view of dashed box in (b,right), showing a cross section through a respiratory septum composed of a fibrocartilage base surrounded by smooth muscle, a large tributary vessel, and respiratory epithelial capillaries. (d) Magnified image of dashed box in (b,left), depicting a small tributary vessel and epithelial capillaries filled with red blood cells. (e) Blood-filled capillaries on the surface of the respiratory septum. (f) SEM section through the respiratory septum, revealing a large tributary blood vessel. A layer of surfactant lines the respiratory epithelium in the air-filled chambers. (g) Magnified image of dashed box in (f,right), showing cross sections through the epithelial capillaries containing red blood cells. (h) Enlarged view of dashed box in (f,left), depicting epithelial capillaries and a cross-section through the air-blood barrier. Abbreviations: AAB, air-blood barrier; AS, air space; C, capillary; CA, main conduit artery; CV main conduit vein; FC, fibrocartilage; GBW, gas-bladder wall; RBC, red blood cell; RS, respiratory septa; S, surfactant; SA, segmental artery; SM, smooth muscle; TV, tributary vessel.

Fig. 5.6 Diagrammatic illustration of the main features distinguishing the four types of fish ventricles. Type I: one myocardial layer (spongiosa) only, no capillaries. Type II: inner spongiosa and outer compacta, coronary circulation, capillaries only in compacta. Type III: similar to type II except capillaries in both myocardial layers. Type IV: larger percentage of ventricle as compacta (> 30%), more extensive capillary system of atrium. The tarpon heart is Type II.

Fig. 5.7 Relationship between dissolved oxygen (PwO2) and aquatic ventilation rate (VR/min) in juvenile Pacific tarpons (n = 10). Data are ± 95% CI. The value of VR declines at low PwO2. The shaded region highlights where opercular stroke amplitude was very low and often visibly imperceptible.

Fig. 5.8 Oxyhemoglobin dissociation curves (means of n = 8 fish) at 25°C for sagor venous blood, Hexanematichthys sagor (= Arius leptaspis). The sagor is a catfish sympatric with Pacific tarpons in some Australian billabongs. Curves are displayed in order of decreasing affinity for O2 from left to right: pH = 8.2, 7.8, 7.4, 6.6. Vertical arrows indicate bottom (left) and surface (right) PO2.

Fig. 5.9 Oxyhemoglobin dissociation curves (means of n = 7 fish) at 25°C for Pacific tarpon venous blood in order of decreasing affinity with declining pH. Curves are displayed in order of decreasing affinity for O2 from left to right: pH = 8.2, 7.8, 7.4, 7.0. Vertical arrows indicate bottom (left) and surface (right) PO2.

Fig. 5.10 Representative traces for a juvenile Pacific tarpon of 364 g displaying measured variables for the time it was in a flume at 27°C. Elevated values for the first 3 h are associated with recovery from surgery. The traces are for swimming speed of 0.27 L/s, except for the shaded region during which it was increased to 1.3 L/s.

Fig. 5.11 Abdominal cavity of a Stage 2 Atlantic tarpon larva of 21.1 mm SL illustrating the well-developed swim bladder, which becomes functional at even shorter lengths. Also see Chapter 1.

Fig. 5.12 Oxygen extracted with each breath by juvenile Pacific tarpons; treatments and statistics as in Fig. 5.13 (see text and source publication).

Fig. 5.13 Air-breathing frequency (fab) of juvenile Pacific tarpons during six successive treatment periods in a respirometer. Vertical bars represent ± 95% CIs.

Chapter 06

Fig. 6.1 Transmission electron micrographs of ionocytes from gills of seawater teleosts. (a) Ionocyte from a common sole (Solea solea) containing numerous mitochondria (m), a tubular system (ts), a subapical tubulovesicular system (tvs; not discussed in the text), and an apical crypt, or pit. (b) apical region of an ionocyte from a mummichog (Fundulus heteroclitus). This cell forms deep tight junctions with surrounding pavement cells (PVCs) and shallow tight junctions with surrounding accessory cells (ACs), which share an apical crypt with the ionocyte.

Fig. 6.2 Model of ionocytes of seawater-adapted teleosts. See text for details. CFTR = cystic fibrosis transmembrane conductance regulator; eKir = inwardly rectifying K+ channel; NHE2/3 = Na+/H+ exchangers, isoforms 2 and 3; NKA = Na+-K+-ATPase; NKCC1 = Na+-K+-CC cotransporter; Rhcg and Rhbg = Rhesus glycoproteins.

Fig. 6.3 Model illustrating how Rh glycoproteins – Rhag (in erythrocyte membranes), Rhbg (in basolateral membranes of gill epithelial cells), and Rhcg (in apical membranes of gill epithelial cells) – might facilitate ammonia excretion from blood to water in gills of freshwater teleosts. Other symbols: CA2 and CA4, carbonic anhydrase genes 2 and 4; NHE2/3, Na+ and H+ exchangers; RBC, red blood cell (erythrocyte).

Fig. 6.4 Model of ammonia excretion by seawater teleosts, illustrating both probable transport mechanisms (active and passive) by transcellular and paracellular paths. Because seawater is well buffered, acidification of gill water is probably not involved in ammonia excretion. Epithelial pavement cells (PVCs) are the most likely sites of excretion. The glycoproteins Rhbg and Rhcg2 are likely restricted, respectively, to basolateral and apical membranes of PVCs, in which case NH3 enters the cytosol (aqueous component of the cytoplasm) via a basolateral Rhbg and leaves by means of the apical Rhcg2. Evidence that NHE2 Na+/H+ exchanger 2) is expressed in the gills of many seawater fishes supports the hypothesis that apical Na+/NH4+ exchange also contributes to branchial ammonia excretion. However, because NHE2 proteins are restricted mainly to ionocytes, which cover a small proportion of gill epithelium, their contribution to the excretion of total ammonia might be small. Ammonia can incidentally enter ionocytes by displacing K+ on the branchial Na+/K+/2Cl– co-transporter or via Na+/K+-ATPase. These two mechanisms are not mutually exclusively. Thus apical Rhcg1, Na+/NH4+ exchange, or both could serve as relief valves promoting removal of ammonia entering ionocytes via these basolateral transport systems.

Fig. 6.5 Relative expression of (a) COX 2, (b) CFTR, (c) NKCC1, and (d) NKA1 mRNA, as measured by quantitative real-time PCR in gills of mummichogs (Fundulus heteroclitus) acclimated to seawater (SW, clear bars) and freshwater (FW, black bars). Values are (± SEM); * = p < 0.05. Note that expression of NKA1 mRNA did not differ between the two solutions.

Fig. 6.6 Relative expression of (a) COX2, (b) CFTR, (c) NKCC1, and (d) NKA1 mRNA measured by quantitative real-time PCR in gills following acute transfer from freshwater (FW, dashed lines) to seawater (SW, solid lines), or the reverse. The different starting expression levels between FW and SW were standardized to the relative acclimation means of Fig. 6.5. Values are (± SEM), n = 5 or 6, * = p < 0.05 for FW → SW transfer, † = p < 0.05 for SW → FW transfer.

Fig. 6.7 Change in total ammonia (as NH4+) excreted along a concentration gradient (ΔNH4+) at the skin of a zebrafish larva: (a) The six locations where ammonia was measured with an ion-selective electrode: 1 snout, 2 pericardial cavity, 3 yolk sac, 4 trunk, 5 cloaca, 6 tail. (b) Mean ΔNH4+ concentration at the six locations (n = 4 larvae).

Chapter 07

Fig. 7.1 Association between aquatic ventilation rate (VR) as opercular movements/min and total sulfide concentration (μM) at 25°C (presumably pooled data for pH values 6.8–7.8). The curve is described by the exponential regression equation VR = e³.⁸⁷⁷–⁰.⁰¹¹x, in which x = μM H2S (n = 73, r² = 0.677, CI = 95%, p < 0.001).

Fig. 7.2 Atlantic tarpon killed by sharks off Coquina Beach, a popular tourist destination at Bradenton Beach, southwestern Florida. The attack occurred about 10:30 am on 2 July 2015, and the remains soon washed ashore.

Fig. 7.3 Unrooted neighbor-joining (N-J) tree showing structure for 15 collections of Atlantic tarpons using pairwise Cavalli-Sforza and Edwards chord distance matrix. Bootstrap support for all nodes < 50%. Collection site designations: United States – North Carolina (NC), Florida west coast (FL), Louisiana (LA), Texas at two locations designated upper and lower (TU, TL); México – Tampico (Ta), Tecolutla (Te) Veracruz (Ve), Chetumal (Ch); Costa Rica (CR); Panamá, Pacific coast (Pa); Puerto Rico (PR); Colombia, Caribbean coast (Co); Brazil, state unspecified (Br); Nigeria, western Africa (Af). Louisiana (LA) apparently was inadvertently omitted in the source publication and thus is not shown here. Total n = 328.

Fig. 7.4 Plot of first two dimensions of a multi-dimensional scaling analysis of genetic affinity of Atlantic tarpons from 15 locations. Collection site designations: United States – North Carolina (NC), Florida west coast (FL), Louisiana (LA), Texas at two locations designated upper and lower (TU, TL); México – Tampico (Ta), Tecolutla (Te) Veracruz (Ve), Chetumal (Ch); Costa Rica (CR); Panamá, Pacific coast (Pa); Puerto Rico (PR); Colombia, Caribbean coast (Co); Brazil, state unspecified (Br); Nigeria, western Africa (Af). Louisiana (LA) apparently was inadvertently omitted in the source publication and thus is not shown here. Total n = 328.

Fig. 7.5 Kinematic sequence of prey capture behavior by juvenile Pacific tarpons. Scale bar = 1 cm.

Fig. 7.6 Kinematic profile of cranial movements observed during prey capture by juvenile Pacific tarpons. Data points represent means of three fish. Time is scaled to time to peak gape (TTPG) to account for variation in time of prey capture. Scaled time, T(0), is the point at which 20% of peak gape is attained at the start of every trial. Vertical error bars are ± SE of scaled time. The single vertical line represents mean time to prey capture from all trials. Symbols: gape, filled circles (black); lower jaw rotation, filled circles (gray); cranial elevation, filled triangles; hyoid depression, clear squares.

Fig. 7.7 Relationship between strike initiation distance and ram speed (m/s). Strike initiation distance is the distance from a fish’s mouth to the prey at start of the strike (i.e. when 20% of peak gape is reached). Each data point represents a feeding trial, and individuals are shown in different symbols. Note how they display variation in range of ram speed and how more variable strike initiation distances are observed at higher ram speeds (r² = 0.79, n = 3).

Fig. 7.8 Schematic representation of a juvenile Atlantic tarpon, illustrating the postero-dorsal cranial inflection.

Fig. 7.9 Representative kinematic profiles of gape, hyoid, and head displacement during prey capture by Atlantic tarpons. None of the three profiles is symmetrical along the abscissa, indicating that the velocity of buccal expansion and opening of the jaw are much faster than the velocity of buccal compression and closing of the jaws.

Fig. 7.10 Relative hyoid depression by degree of head lift (HL) correlates significantly with Reynolds number in suction feeding by zebrafish and decreases with ontogeny. When adjusted for body length (TL), relative hyoid depression is greatest in first-feeding larvae, declining in older stages. Reynolds number and relative hyoid depression are related inversely: first-feeding larvae (3–4 mm TL); metamorphosing larvae (6–7 mm TL); juveniles (10–12 mm TL); adults (25–27 mm TL). Number of trials representing the mean values, form of the variance, and sample size unstated. Regression equation: y = 0.001x + 0.217, r² = 0.88.

Chapter 08

Fig. 8.1 Team tournament fishing for Atlantic tarpons in southwestern Florida. The boat has been painted with the names and logos of the team’s commercial sponsors, and a television camera crew films the action.

Fig. 8.2 Tarpon tournament fishing as a sporting event, complete with beer advertisements painted directly on the boats (Fig. 8.1) and pin-up girls.

Fig. 8.3 Feeding the tarpons at Robbie’s Marina, Islamorada, Florida.

Fig. 8.4 This illustrates inappropriate catch-release technique. Avoid handling a tarpon and lifting it out of the water.

Fig. 8.5 Another questionable catch-release procedure. No empirical evidence indicates that walking a tarpon prior to release or attempting to otherwise resuscitate a tarpon or any other fish is beneficial.

Fig. 8.6 Annual post-release mortality of Atlantic tarpons in the US recreational fisheries from 2000–2010. Dotted lines represent 95% CIs. Mean mortality was calculated using short-term catch-release deaths of 13%, representative of Florida’s Gulf Coast recreational fishery and included post-release shark predation. Also see Guindon (2011).

Fig. 8.7 Parts of a circle hook. (a) Basic components. (b) General specifications: A, width; B, length; D, gap; E, throat; F, front length; W, point angle; G, front angle; H, offset angle; Ø, wire diameter. Lettering conforms to hook manufacturer conventions. Specifications for a true circle hook: angle of point to shank must be a minimum of 90°; angle of front length must bend a minimum of 20° toward shank; front length of hook should be 70–80% of hook’s total length.

Fig. 8.8 Schematic illustrations of how a circle hook works when pressure is applied to the line (lateral and frontal perspectives). (a) The fish ingests the bait and starts to swim away (or the angler applies gentle pressure). (b) The hook is pulled to the side of the mouth, where its point catches the flesh at the jaw and pivots outward with increasing pressure. (c) At a critical line tension, either by the fish’s swimming or the angler giving a tug, the hook slides over the jaw and rotates, becoming embedded. Unlike J-hooks, circle-hooks do not require a hard yank on the line to become set in a fish’s jaw. Only gentle pressure is usually required, and tugging too hard is likely to cause foul-hooking.

Fig. 8.9 Dead tarpons strung up.

Fig. 8.10 Values for: (a) muscle lactate, (b) blood lactate, and (c) blood glucose in post-exercise juvenile Pacific tarpons subjected to five treatments: (1) aquatic normoxia, slow-swimming, air access; (2) aquatic normoxia, fast-swimming, air access; (3) aquatic normoxia, fast-swimming, air denial; (4) aquatic hypoxia, fast-swimming, air access; (5) aquatic hypoxia, fast-swimming, air denial. Swimming speeds were 0.1 m/s (slow) or 0.3 m/s (high). Dissolved oxygen was either 20.8 kPa (normoxia) or 6.1 kPa (hypoxia). Data represent ±SD.

Fig. 8.11 Relationship between blood and muscle lactate for juvenile Pacific tarpons under functional and environmental normoxia and hypoxia from the five groups (Fig. 8.10) Data represent ±SD (n = 6). Curve fit: y = 0.27x – 2.05.

Fig. 8.12 Hematological values for (a) hematocrit, (b) hemoglobin, (c) mean cell hemoglobin concentration (MCHC), and (d) caudal venous pH (pHcv) in juvenile Pacific tarpons swum to exhaustion and allowed to recover for 4 h, with and without access to air. Data represent ±SD (n = 6).

Fig. 8.13 Wall panel of tarpon scales signed by anglers fishing out of the Tarpon Inn, Port Aransas, Texas. They reveal the lengths and weights of fish caught through the years.

Fig. 8.14 A scale from the wall signed and dated by US President Franklin D. Roosevelt 8 May 1937.

Fig. 8.15 Comparison of numbers of Atlantic tarpons landed by recreational anglers at Useppa Island, Boca Grande Pass, on Florida’s southwestern coast (broken line) and Port Aransas, Texas (solid line).

Fig. 8.16 Loggerhead sea turtle (Caretta caretta) nest on Longboat Key, Florida located and identified by Mote Marine Laboratory staff members and volunteers. Stakes mark the nest’s perimeters; notes on the stakes record the date the eggs were laid and the expected hatch date.

Tarpons

Biology, Ecology, Fisheries

Stephen Spotte

Mote Marine Laboratory

Sarasota, Florida, USA

This edition first published 2016, © 2016 by John Wiley & Sons, Ltd

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Library of Congress Cataloging-in-Publication Data

Names: Spotte, Stephen, author.

Title: Tarpons : biology, ecology, fisheries / Stephen Spotte.

Description: Chichester, UK ; Hoboken, NJ : John Wiley & Sons, 2016. | Includes bibliographical references and index.

Identifiers: LCCN 2016003051| ISBN 9781119185499 (cloth) | ISBN 9781119185703 (epub)

Subjects: LCSH: Tarpon. | Tarpon fisheries.

Classification: LCC QL638.M33 S66 2016 | DDC 597.5/7–dc23

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Cover image: Atlantic Tarpon © 1992, Diane Rome Peebles

Preface

Two species of tarpons exist today, one in the Atlantic (Megalops atlanticus), the other (M. cyprinoides) in the Indo-West Pacific region. The name tarpon, or tarpom, is apparently of New World origin. The Englishman William Dampier encountered tarpons on his first voyage to the Bay of Campeche (which he called Campeachy), México, and his mention of the Atlantic tarpon is one of the earliest. Dampier wrote about the fish in his journals in 1675 and later included these entries in the account of his voyages around the world. The copies of Dampier’s Voyages cited here are early twentieth-century editions edited by the poet John Masefield, but earlier versions were published in the seventeenth and early eighteenth centuries. In Volume II, Dampier (1906: 117–118) stated: The Tarpom is a large scaly Fish, shaped much like a Salmon, but somewhat flatter. ’Tis of a dull Silver Colour, with Scales as big as a Half Crown. A large Tarpom will weigh 25 or 30 Pound. Because of their extensive distributions, both species have numerous other common names in many languages.¹ For simplicity, I refer to them as Atlantic and Pacific tarpons. The Pacific species is also called the Indo-Pacific tarpon and oxeye (or ox-eye), or sometimes oxeye (ox-eye) tarpon or herring.

Atlantic tarpons grow large, reaching 2.5 m and weighing 150 kg. The Pacific species is comparatively small, attaining only 0.6 m and 3 kg, although unsubstantiated reports exist of specimens three times this length (Seymour et al. 2008 and references). Despite the size disparity, their morphology, physiology, ecology, developmental biology, and other life-history features are so similar that I often found little justification for separate treatments, although I have separated them when possible for clarity. In some instances, such as discussion of distributions, I was handicapped by limited access to literature on the Pacific form.

Previous books have concentrated on just a few aspects of tarpon biology or restricted discussion to the Atlantic tarpon recreational fishery. My objective is to cover these and other topics without being too tiresome. The angling aspect presented (Chapter 8) is not about how to catch tarpons but how to conserve them and, if you must catch them, how best to do so with minimal stress to the fish and then release it in a manner offering the best chance of long-term survival.

My presentation of tarpon biology derives from a broad perspective, one in which I hope to assess the tarpon’s unique life-history in terms of fishes generally. Books like this are usually written by groups of specialists, the result being a series of chapters in which different aspects are partitioned, handed to separate authors, and subsequently treated in isolation. The result is often uneven, redundant, incompletely integrated, and fails to view the subjects themselves – tarpons in this case – as entities ruled by common natural forces for which data from more extensively studied species can sometimes apply just as well. Every biography is, in the end, a narrative of heritage and commonality.

My objective as a single author is to provide a cohesive picture of tarpon biology, ecology, and fisheries in which specialty aspects usually compartmentalized (e.g. physiology, larval development) blend at the edges and reinforce one another. I hope to accomplish this without loss of accuracy. For example, variations on the cube law used to practical advantage in fishery biology for predicting length and weight of individual fishes and assessing the condition of populations also apply theoretically to certain facets of water circulation in the buccal cavity (i.e. lamellar length scales isometrically with body weight). To receive full benefit of this integrative approach, chapters need to be read in sequence. This book, like my others, has been designed to be read, not consulted. Skipping through the text and examining sections out of sequence is guaranteed to be less satisfying. The reader has been duly advised, and I offer no apologies.

Symbols and abbreviations are generally defined at first use, but a roster of them is provided in the book’s front matter. Background information necessary to understand certain concepts is given either superficially in the text or, if more detail is necessary, in occasional footnotes. The presentation overall assumes a certain advanced level of knowledge.

An early anonymous reviewer made the reasonable suggestion that I include a section on tarpon evolution. However, not being an ichthyologist I felt uncomfortable doing so. I therefore left this subject and certain other avenues of specialization (e.g. detailed aspects of tarpon skeletal anatomy) to the experts. I take a systems approach instead, integrating functional biology with ecology, and discussing both disciplines in terms of effects caused by humans in the recreational and commercial fisheries at both the individual and population level. Only a few reports exist on tarpon physiology, although other species can safely be used as proxies at the system and even cellular level, at which point any differences are of degree, not kind.

Tarpons are distributed widely throughout subtropical and tropical waters around the world. Appendix A at the end of the book comprises a partial list of countries from which both species have been recorded in the literature. Pusey et al. (2004) provided an outstanding short summary of the Pacific tarpon’s natural history. Nothing I found on the Atlantic species in the recent literature matches it for brevity and completeness. Hildebrand’s (1963) treatment came closest, but his information is outdated.

The Atlantic tarpon ranges north to Nova Scotia and south to Brazil. Some authors extend its southern range to the coast of Argentina (e.g. Castro-Aguirre et al. 1999: 89; Gill 1907: 36; Hildebrand 1963: 119), although I was unable to find a published record of its presence in either Uruguay or Argentina (e.g. Bouyat 1911 did not mention it). The warm, south-flowing Brazil Current stops at the mouth of the Río de la Plata, and the sea beyond, including off Patagonia, is temperate. It seems that any Atlantic tarpons found there could only be stragglers from Brazil.

Reports about the tarpon in the eastern Atlantic are uncommon in the refereed literature, aside from its inclusion in species lists or as notes mentioning its appearance in regional ichthyofauna. Tarpons in the eastern Atlantic range north to the Formigas, a group of small islands in the eastern Azores (Costa Pereira and Saldanha 1977) and the inshore waters of continental Europe including the Tagus River estuary of Portugal (Costa Pereira and Saldanha 1977), the Lee River of Cork County, Ireland (Twomey and Byrne 1985; Wheeler 1992), and the French Basque coast (Quero et al. 1982: 1022–1025). I could not find specific mention of Atlantic tarpons entering the Mediterranean, but surely they have.

Minimum water temperatures probably influence the distributions of Atlantic tarpons (Killam (1992: ix). Costa Pereira and Saldanha (1977) pointed out that north of Sénégal and south of Angola sea temperatures begin to cool and salinity rises, conditions they believed restrict the tarpon’s latitudinal range in the eastern Atlantic. These regions are characterized by heightened rates of surface evaporation, lower seasonal rainfall, and weak fluvial flow into the Atlantic, factors that combine to keep coastal salinity values high and perhaps discourage inshore migration of metamorphosing tarpon larvae. Lower sea temperatures both to the north and south are the result of increasing latitude. The only elopiform listed by Penrith (1976) from Namibia and all of South Africa’s western coast was the bonefish (Albula vulpes). Evidently this region falls outside the Atlantic tarpon’s southern latitudinal range.

Costa Pereira and Saldanha (1977) did not mention that between Sénégal and Angola, where the skull of the African continent curves eastward, are sandwiched 13 countries with coastlines characterized by warm seas, high seasonal rainfall supporting tropical forests, mostly strong fluvial flow, an abundance of swamps and brackish lagoons, and other environments favorable for tarpons. The Atlantic tarpon’s range is likely to be extended to southeast Asia at some future time now that specimens have been imported into Thailand and released into recreational fishing reservoirs (Chapter 7.2). Some individuals will inevitably escape into coastal waters or be released there. Atlantic tarpons are already established on the Pacific coasts of Panamá and Costa Rica,² having traversed the Panamá canal after its opening in 1914 (Anonymous 1975; Hildebrand 1939).

The Atlantic tarpon is essentially a straggler outside the subtropics, but the Pacific tarpon’s normal range north and south seems broader, perhaps extending routinely into temperate waters. Wade (1962: 593) gave a latitudinal range in the western Pacific as Hamana Lake, Totomi Province, Japan (34.7°N, 137.6°E) to Victoria, Australia (≈37.0°S, 144.0°E). East to west, the species ranges halfway across the globe, from Tahiti in the Society Islands (17.7°S, 149.4°W) to Durban, South Africa (29.9°S, 31.0°E). Wade (1962: 594) gave its epicenter of abundance as the region encompassing India, Ceylon, the Malay Archipelago, East Indies, southern Philippine Islands, and Polynesia. Ley (2008: 3) offered a similar range: 28°N (Japan) to 35°S (southern Australia and