JOURNAL OF THEWORLD AQUACULTURE SOCIETY

Vol. 41, No. S1February, 2010

An Efficient Technique for the Captive Breeding of anEndangered Freshwater Fish Salaria fluviatilis (Pisces:

Blenniidae), with a Description of Its Ontogeny

Fatima Gil

Aquario Vasco da Gama, R. Direita, Dafundo, P-1495 Lisboa Portugal

Claudia Faria1 and Vıtor Carvalho Almada

Unidade de Investigacao em Eco-Etologia, Instituto Superior de Psicologia Aplicada,R. Jardim do Tabaco 34, P-1149-041 Lisboa Portugal

AbstractSalaria fluviatilis is one of the few freshwater members of the family Blenniidae and occurs

around the Mediterranean Basin. This species is vulnerable or endangered in most countries where itoccurs. Thus, information on its developmental biology and the establishment of methods for ex situreproduction of highly endangered populations, to preserve them until natural habitats are restored,are much needed. A technique for the culture of this endangered species in controlled conditions ispresented, together with the description of the full developmental sequence, from egg to adult. The useof the rotifer Brachionus calyciflorus at the onset of exogenous feeding proved to be an efficient wayto allow larvae to reach the size when they can feed upon Artemia nauplii. Embryonic developmentlasted 12–14 d at 20–21 C. Newly hatched larvae measured 5.1 mm total length (TL). The mouthand anus were opened; the eyes were pigmented; there were almost no yolk; and the pectoral finswere small and unpigmented. Most larvae settled at 13.0–14.0 mm TL (27–31 d after hatching) andshowed full juvenile pigmentation patterns at 27.0–28.0 mm TL (83 d after hatching). The larvae ofthis species showed agonistic behaviors once they began to settle.

Salaria fluviatilis (Asso 1801) is a freshwatermember of the blenniid family that lives inrivers and lakes in the Mediterranean Sea basinand also in Portugal (Oliveira et al. 1992; Criv-elli 1996). Although there are many studiesabout the ecology of this species (e.g., Freemanet al. 1990; Cote et al. 1999; Vinyoles et al.1999, 2002), there is little information about itsdevelopmental biology. For the Iberian Penin-sula, Vinyoles and De Sostoa (2007) describedthe life-history traits of this species. Sexualmaturity is attained during their first year oflife and females spawn multiple times duringthe breeding season. The breeding period isfrom May/June to August (Vinyoles and DeSostoa 2007). The demersal eggs are individu-ally attached to the underside of a rock, or other

1 Corresponding author.

protected substratum, and formed single layeredpatches. They are guarded and aerated by themale until hatching. Typically, several femalesspawn in the same nest so that at a given timeeach male is guarding eggs at several develop-mental stages (Wickler 1957). S. fluviatilis isclassified as vulnerable or endangered in themajority of the countries where it occurs (seeVinyoles and De Sostoa 2007). It is listed in theAppendix III of the Berne Convention, in theAppendix II of the Habitats Directive and islisted as Endangered in the Portuguese and theSpanish Vertebrate Red Data Books (SNPRCN1992; Doadrio 2002), because of habitat loss,water pollution, the introduction of exoticspecies, and excessive water extraction (Elvira1995; Collares-Pereira et al. 2000; Hernandezet al. 2000). There is an urgent need to designand implement effective management and con-servation measures to recover this endangered

© Copyright by the World Aquaculture Society 2010

49

50 GIL ET AL.

freshwater species. The information concerningits developmental biology is of much need toallow captive breeding when necessary for therecovery of natural populations. A major prob-lem in rearing this species is that, in line withits origin from marine ancestors, S. fluviatilisretains a planktonic larval phase, which makesthe techniques commonly used to rear mostfreshwater fishes unsuitable. In this article, atechnique for the culture of S. fluviatilis in cap-tivity is presented, together with the descrip-tion of the full developmental sequence of thisspecies, from egg to adult.

Material and Methods

Eggs and larvae were obtained from a captivegroup of 11 fish (5 males and 6 females), main-tained in captivity since March 2007 at a publicaquarium, Aquario Vasco da Gama (Lisbon).This stock was kindly provided by Profes-sor Eduardo Barata (University of Algarve),and had been collected 3 yr before at LagunaBanoles (Cataluna, Spain). The 600 L tank (200× 50 × 60 cm) was illuminated with a fluores-cent light (60 W) from 0900 to 2100 h. Bothmechanical (powerhead with cartridge attach-ment; 1500 L/h) and biological (undergravelfilter with airlifts) filters were used. In addi-tion, one-third of the tank water was changedonce a week (water quality parameters: NH+

4 =0.013 mg/L, range: 0.002–0.031 mg/L, n = 5;pH = 8.05, range: 7.85–8.20, n = 5; dissolvedoxygen = 5.44 mg/L, range: 5.10–5.90 mg/L,n = 5). The bottom of the tank was coveredwith a sand layer and several flat stones wereprovided as shelter and breeding sites. Temper-ature varied between 20 and 23 C. The adultswere fed ad libitum once a day with choppedmussel and blood worm larvae.

The complete sequence of embryonic devel-opment was based on one batch spawned under

a flat stone on April 17, 2007 (average tem-perature = 21C, SD = 0.74, range: 20–21 C,n = 14). A sample of eggs was removed dailyfrom the stone guarded by the male, by aspi-ration with a long pipette. The eggs wereobserved under a Nikon Stereomicroscope, pho-tographed by a Moticam 2300 Digital Cameraand preserved in buffered 5% formalin. The eggcapsules were opened and the embryos weredistended to allow more detailed observations.

Full larval development was described fromtwo other batches that hatched on June 12, 2007(water temperature = 21C) and July 16, 2007(water temperature = 22C). The rearing proce-dure was run twice. Upon hatching, the plank-tonic larvae were collected with a small glassand individually transferred to the rearing tanks.Each rearing tank was stocked with about 400newly hatched larvae. These were 30 L glasstanks (40 × 30 × 25 cm), and each were illu-minated with a fluorescent light (18 W) 24 h perday (the light was 4 cm above the tank cover).All the tank walls, except the one in the front,were painted black. A constant flow of water (2L per hour) was maintained. Larvae were fedthree times a day with a mixture of small sizefreshwater rotifers, Brachionus calyciflorus, andalgae, Scenedesmus sp. (10 mL), maintaining aconcentration of 4–8 rotifers/mL in the rear-ing tank. The third meal, which was deliveredduring the night, was dispensed by a drippingsystem to ensure a gradual delivery. After Day37, these mixtures were enriched with decap-sulated eggs of Artemia sp, with 0.2 mm width(20 mg each time) (Brine Shrimp Direct). AfterDay 49, they were also fed with blood wormlarvae (700 mg each time). After Day 64, theywere fed three times a day with decapsulatedArtemia eggs and two times a day with a mix-ture of blood worm larvae and chopped mus-sel (see Table 1). After Day 96, the diet was

Table 1. Feeding regime of the rearing tanks.

Alga RotifersDecapsulatedArtemia eggs

Blood wormlarvae

Choppedmussel

Item concentration — 4–5 rotifers/mL 20 mg 700 mg 100 mgFeeding schedule Three times a day Three times a day Three times a day Two times a day Two times a dayFeeding days D1–D63 D1–D63 D37–D95 D49–D95 D64–D95

CAPTIVE BREEDING AND ONTOGENY OF SALARIA FLUVIATILIS 51

replaced by that of the adults. The reared tankswere cleaned daily, before the first feeding, byaspiration of the bottom with an acrylic tubeof 4 mm of internal section. Once a week, thewalls of the tank were cleaned with a razorblade to remove the algal film.

The algal stock was isolated and regularlycultured in Aquario Vasco da Gama. Conical14 L acrylic tanks were employed. Each culturewas started with 5 L of a pre-existing cultureand 9 L of tap water, which was allowed torest for at least 2 d. Fourteen milliliters of Con-way medium were added to the tank as fertil-izer. Temperature was kept at 19–22 C and thetanks were illuminated 22 h per day with fluo-rescent lights (40 W). Algal concentration wasnot controlled, but each culture was consideredready for use after about 8 d, if the water dis-played an intense green color. The same tanks,and light regime, were used for the rotifer cul-tures. In this case, the temperature was kept at22–24 C. Each day, 2 L of rotifer culture wasremoved and sieved, with a net of 45 μm mesh.This volume was replaced by an equivalentvolume of the algal culture described above.Rotifer concentration ranged between 5 and 86rotifers/mL.

An unexpected mortality was detected whenthe fish were about 3 wk old and saltwaterwas added to the water and salinity was keptat 2.2‰ from Day 21 to Day 114. Larvaewere collected daily, anesthetized using Ethy-lene Glycol Monophenyl Ether Merck (less than1 mL) and photographed until metamorphosis.After metamorphosis, juveniles were kept in thesame tanks but light intensity was reduced dur-ing the night, with a semi-opaque screen, andstones were placed on the bottom to provideshelter. All larval measurements correspond tototal lengths (TLs).

Results

Captive males guarded egg batches fromApril to September (two to three males at eachtime). All adults survived. In each nest, therewere simultaneously eggs at several develop-mental stages. Recently laid eggs were whitish,and in subsequent days they became more

A

B

C

Figure 1. Eggs collected at different developmentalstages: (A) Day 3: embryo differentiation; (B) Day 8:embryo with mouth differentiated; (C) Day 12: embryojust prior to hatching.

brownish. They were semi-spherical (Fig. 1)and had a flat attachment disk. The major axiswas 1.2 mm (SD = 0.05, range: 1.1–1.2 mm,

52 GIL ET AL.

Table 2. Ontogenetic events of embryonic development of Salaria fluviatilis in order of first appearance (days afterhatching): (1) embryo recognizable; (2) cephalic and caudal dilatation; (3) eye lens; (4) brain; (5) notochorddifferentiation; (6) myomeres; (7) beginning of pigmented eyes; (8) tail bud free of the yolk; (9) auditory vesicules; (10)gut differentiation; (11) median finfold; (12) otoliths; (13) anus visible but closed; (14) pectoral fin buds; (15) mouthdifferentiation; (16) mouth visible but closed; (17) anus opened; (18) opercula differentiation; (19) mouth opened; (20)hatching glands; (21) opercula opened; (22) hatching. Temperature range: 20.00–21.00 C.

Events 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22Days 2 2 3 3 3 3 3 3 3 3 5 5 5 6 7 8 10 11 11 12 12 13

n = 10) and the minor axis was 0.7 mm (SD =0.03, range: 0.7–0.8 mm, n = 10). Embryonicdevelopment lasted 12–14 d at 20–21 C.

The main ontogenetic events of embryonicand larval development are shown in Tables 2and 3, respectively.

Newly-hatched larvae (Fig. 2A) measured5.1 mm TL (SD = 0.07, range: 5.0–5.1 mm,n = 10). The anus and mouth were open,with formed lips and differentiated jaws. Theyolk was almost fully absorbed. The liver wasdeveloped and the eyes were fully pigmented.The opercula were open, and the sagittae andlapilli otoliths were visible. The pectoral finswere small and rounded, without any rays orpigmentation.

Newly-hatched larvae had a heavy peritonealpigmentation. Ventrally there was a melano-phore near the anus and a series of melano-phores at the posterior half of the larvae.Dorsally, there were many melanophores on thehead and internally at the otic vesicules. Therewas also an internal row of melanophores frombehind the eyes to the gut. The base of the pec-toral fins presented one ramified melanophore.There was also some diffuse yellowish pigmen-tation all over the head and at the base of thepectoral fins.

The pigmentation pattern was maintainedduring development, with an increase in thenumber and intensity of melanophores at theventral row, in front of the liver, and at the cep-halic region and opercula (see Table 3).

The juvenile pigmentation (Fig. 2D) appe-ared at 26.0–28.0 mm TL (83 d after hatching).The head, lips, opercula, anterior part of thebody, and the base of the pectoral fins wereheavily pigmented. There was a dark band thatextended from the upper lip to the lateral side ofthe head above the eye. There were dark spots

along the dorsal and ventral mid-line. The dor-sal, caudal, and the posterior anal fin rays werepigmented. There were also melanophores onthe bases of the caudal and anal fins. On thepectoral fins, there was a transverse band ofmelanophores in the middle of the fin and therewere melanophores along the lower rays.

Newly-hatched larvae presented a relativelysmall preanal length (29% of SL). At 7.0 mm(5 d after hatching), the larvae possessedtwo to four preopercular spines. At 11.0 mmTL (18–20 d after hatching), the total num-ber of vertebrae was 36–37, excluding theurostyle (10 preanal vertebrae) and all finrays were present (D = XII–XIII + 16–20;A = II + 17–21; V = I + 3; P = 12–14). At8.6–9.0 mm TL (12 d after hatching), the noto-chord flexion was completed (Fig. 2B).

The change to a benthic mode of life wasgradual. At 11.2 mm TL (20 d after hatch-ing), fish began to contact the aquarium bottom.Gradually they spent longer times at the bot-tom, until they permanently settled. Most fishsettled at 13.0–14.0 mm TL (27–31 d afterhatching), before acquiring juvenile pigmenta-tion (Fig. 2C). At this time, they began to showagonistic behaviors, like charging (one fish infront of another bends its body in an “S” pos-ture and charges, a movement similar to theone used to capture prey items), butting on thecaudal fin of another fish, chasing, and fleeing.Fish measured 22.0–23.0 mm TL (n = 26) 48d after hatching, 28.0–29.0 mm TL (n = 25)82 d after hatching, and 46.0–48.0 mm TL(n = 25) 210 d after hatching. Some fish beganto show the crest on the head, typical of males,86 d after hatching, and 112 d after hatching allmales had already a conspicuous crest. As theadults were kept in groups and the eggs wereguarded by the males under stones, estimation

CAPTIVE BREEDING AND ONTOGENY OF SALARIA FLUVIATILIS 53

Tab

le3.

Ont

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etic

even

tsof

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Sala

ria

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ng):

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edin

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ys;

(3)

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eope

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ines

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ctor

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;(7

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elan

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wer

rays

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over

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the

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eba

seof

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;(1

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eth;

(11)

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km

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(12)

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ys;

(13)

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alfin

rays

;(1

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;(1

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(22)

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row

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plet

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3)m

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infr

ont

ofli

ver;

(24)

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tla

rvae

sett

led

onth

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;(2

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pica

lju

veni

lepi

gmen

tati

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(TL

)to

tal

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th.

The

two

batc

hes

used

for

larv

alde

velo

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tw

ere

mer

ged.

Tem

pera

ture

rang

e:21

.00

–23

.00

C.

Eve

nts

12

34

56

78

910

1112

1314

1516

1718

1920

2122

2324

25D

ays

23

35

66

6–

86

–8

6–

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10–

1212

1212

1214

15–

2015

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2027

27–

3127

–31

27–

3127

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83T

L(m

m)

5.1

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27.

0–

7.5

7.6

–9.

09.

0–

13.5

26.0

–28

.0 of egg mortality was not attempted to avoiddisturbing the guarding fish. During the 31 d oflarval development, mortality was about 85%in each tank. Juvenile mortality was 20%. Atotal of 48 juveniles were still alive at the endof February 2008.

Discussion

The developmental sequence described inthis study agrees in general with those describedfor other blenniid species and may be useful toidentify larvae collected in the plankton (e.g.,Olivar 1986; Sabates 1994; Faria et al. 2002,2005, 2006). Although S. fluviatilis presents anumber of traits that could be advantageousto survive in unstable environments, such asa long spawning period, multiple spawnings,and parental care of the eggs by the males(Vinyoles and De Sostoa 2007), it seems to bevulnerable to many anthropogenic disturbancesthat affect Mediterranean type streams (Elvira1995; Collares-Pereira et al. 2000; Hernandezet al. 2000). When compared with other fishthat inhabit the same environments, namelycyprinids (e.g., Carvalho et al. 2003), the devel-opment of S. fluviatilis is remarkable for thepresence of almost a month of planktonic lar-val life, a feature probably inherited from itsmarine ancestors (most blenniids are marine)(Nelson 2006). In fluvial systems, planktoniclarvae must run a high risk of downstream drift-ing, which may drive them to unfavorable habi-tats. Moreover, many freshwater systems havereduced depths. In these circumstances, larvaeare at short distances both from the surface andthe bottom, a condition which could increasethe spectrum of potential predators. Fischer andKummer (2000) suggested that one of the keyissues to the conservation of this endangeredspecies is the preservation of intact flow con-ditions in the rivers. This may be important toavoid siltation of the nests, but as suggested bythe present results, must be sufficiently weakto avoid downstream transport of the larvae.The increasing unpredictability of flow regimesin Mediterranean rivers, apparently associatedwith the current climate change, is causingsevere summer droughts, which are aggravated

54 GIL ET AL.

A

B

C

D

Figure 2. Larvae collected at different developmental stages: (A) Day 1: newly hatched larvae (5.1 mm TL); (B) Day 15:9.2 mm TL; (C) Day 27: 13.2 mm TL; (D) Day 83: juvenile (28.0 mm TL).

CAPTIVE BREEDING AND ONTOGENY OF SALARIA FLUVIATILIS 55

in many places by water extraction. Thesedroughts and flooding at unusual periods maybe a major risk for this species.

The duration of the larval planktonic stagealso means that during their first month oflife, fish are unable to control their movementsto reach benthic prey, and thus depend onzooplankton of suitable size in the watercolumn. On the other hand, when they hatchthe larvae are too small to feed upon youngdaphnia or artemia nauplii. We believe that akey to the success of this culture experimentwas the use of a stock of small-sized freshwaterrotifers during the first 2 wk of larval growth.Although microalgae were added to the rearingtanks with the aim to keep the nutritional valueof the rotifers, they were observed in the guts oflarvae during the first week in the rearing tanks,so we cannot rule out the possibility that thealgae were also been used as food by the fish.Future studies, aimed to clarify this question,could help to optimize the diet for rearing thelarvae of this endangered fish.

Although larval mortality was high, it isimportant to remember that males of thisspecies, which are of small size, can guardthousands of eggs in a season (Wickler 1957).Moreover, if a sufficient number of nests isprovided, a considerable number of guardingmales can be kept per square meter (threemales with nests per square meter in our set-up). Thus, although we consider that additionalstudies are needed to reduce larval mortality,the present protocol is sufficient to producethousands of juveniles in a season, even if spacefor broodstock is limited to a few square metersof tank area.

Acknowledgments

This study was supported by Fundacao paraa Ciencia e Tecnologia (FCT) as part ofPluriannual Program (UI&D 331/94, partiallyFEDER funded) and by FCT and FEDER aspart of the project POCTI/BSE/46825/2002.C. F. was also supported by a grant fromFCT (SFRH/BPD/26939/2006). We would liketo thank the technicians of Aquario Vasco daGama for the help in tank maintenance, Rita

Lourenco for the illustrations and L-IPIMARfor the supply of a freshwater rotifer sampleand maintenance technique.

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