The use of otolith shape analysis for ageing juvenile red snapper, Lutjanus campechanus

Morphological changes in otolith shape with age, of young (<age 3) red snapper were examined through shape analysis and tested as an objective method for age determination. Otoliths from two collections of juvenile fish (hatchery and wild) were used in the study. First, shape analysis was applied to a series of known-age otoliths from hatchery-reared age 0, 1 and 2 fish. Multidimensional scaling and non-parametric analysis of similarities showed significant shape differences among the three age classes of fish. Discriminant function analysis and cross-validation classification showed 65.6% correct age classification based on shape variables alone, and 86.7% correct age classification with inclusion of otolith weight in the discriminant function (n?=?90). Subsequently, the method was applied to otoliths from a series of age 0, 1 and 2 wild caught red snapper. Otoliths from wild fish showed a similar age classification success rate of 68.9% based on shape variables alone and 86.7% correct age classification with the inclusion of otolith weight in the discriminant function (n?=?90). Ageing of juvenile red snapper through otolith increment counts has been difficult in past studies and this study provides an alternative, objective method of otolith shape analysis for ageing young fish of this species.     

Effects of tag type on red snapper Lutjanus campechanus tag retention,growth and survival under hatchery conditions

Management of red snapper stocks is one of the most controversial issues in the Gulf of Mexico fisheries. Fish tagging programs can help to address many management issues if an appropriate tag is selected. In the study three types of tags were tested to determine tag retention and effects on red snapper growth and survival. Hatchery‐produced juveniles (43.7 ± 5.6 g) were either not tagged or given: internal anchor tags anchored in the abdominal cavity; passive integrated transponders (PIT) tags injected into the body cavity; or metal self‐piercing fish tags clamped around the dentary bone. Fish were stocked at 25 m^?3 in three replicate circular tanks/tag type, and fed a commercial feed for a 150 days period. Fish survival did not differ by treatment. Average weight gains after 150 days were similar. Tag retention differed by treatment (P = 0.0002), with 100% retention of PIT tags, 98.4 ± 2.8% retention of jaw tags, and 90.4 ± 1.6% retention of internal anchor tags. Loss of internal anchor tags occurred primarily within the first month. Inflammation was frequently observed at the internal anchor tag insertion site. Irritation and cell proliferation was sometimes observed in areas around the jaw tags.     

Mycoses in red snapper (Lutjanus campechanus) caused by two deuteromycete fungi (Penicillium corylophilum and Cladosporium sphaerospermum)*

We report two species of deuteromycete fungi (Penicillium corylophilum and Cladosporium sphaerospermum) concurrently infecting the swim bladder and posterior kidney and causing erratic behavior in two specimens of wild-caught, tank-held red snapper (Lutjanus campechanus). Lesions produced by both species infiltrated the immediately surrounding tissue and produced severe pathological changes; however, the infection apparently was not systemic. Only P. corylophilum grew in the initial culture from the swim bladder and only C. sphaerospermum grew in the initial culture from the kidney. Infection may have occurred upon penetration of a syringe to deflate the swim bladder. There was no horizontal transmission to 13 other specimens of red snapper held in the same tank. This suggests that these fungi are not primary pathogens. Injection of each species into various sites in the Gulf killifish, Fundulus grandis, failed to produce infections within 1 month, suggesting differences in susceptibility among species.     

Susceptibility and tolerance of spotted seatrout, Cynoscion nebulosus , and red snapper, Lutjanus campechanus , to experimental infections with Amyloodinium ocellatum

Amyloodinium ocellatum is a parasitic dinoflagellate that infects warm-water marine and estuarine fishes and causes mortalities in aquaculture. Its life cycle consists of 3 stages: a feeding trophont that parasitizes the gills and skin where it interferes with gas exchange, osmoregulation, and tissue integrity; a detached reproductive tomont; and a free-swimming infective dinospore. We compared the susceptibility and tolerance of juvenile spotted seatrout, Cynoscion nebulosus, and red snapper, Lutjanus campechanus, to this parasite by individually exposing fish in 3-L aquaria (at 25 C and 33 practical salinity units) to several dinospore doses over different time periods and quantified the size and number of resulting trophonts. We estimated the trophont detachment rate and trophont size at detachment, the 24-hr dinospore infection rate, the dinospore 48-hr median lethal dose (LD(50)), and the trophont lethal load at the 48-hr LD(50). There were no significant differences in dinospore infection rates or dinospore lethal doses between spotted seatrout and red snapper; however, trophonts remained attached longer and attained a larger size in red snapper than in spotted seatrout. The trophont lethal load was significantly higher in spotted seatrout than in red snapper. A proposed model simulating the trophont dynamics reflected our experimental findings and showed that A. ocellatum reproductive success is linked both to the number of dinospores and the size of the trophont, factors that, in turn, are linked to the time the trophont spends on the host and the number of trophonts the host can tolerate.     

Historical and contemporary evidence of a mutton snapper (<Emphasis Type="Italic">Lutjanus analis</Emphasis> Cuvier, 1828) spawning aggregation fishery in decline

Scientific information on reef fish spawning aggregation fisheries is sparse in light of numerous regional declines and extirpations from overexploitation. Fisher interviews of the small-scale commercial mutton snapper (Lutjanus analis) spawning aggregation fishery at Gladden Spit, Belize, suggests a historic decadal decline. The reported trend is supported by analysis of inter-seasonal catch and effort and yield (2000–2002) that reveals a 59% decline in catch per unit effort (CPUE) and a 22% decrease in mean landings per boat. Declining population-level trends are also supported by a significant decrease in inter-annual median lengths of mutton snappers (2000–2006). These findings demonstrate the need for additional life history information that includes length-associated age and details on growth to provide clearer support of the effects on, and responses by, populations following fishing. In view of the historical changes to mutton snapper CPUE and landings at Gladden Spit and the fishery-associated declines in fish spawning aggregations observed globally, a precautionary approach to spawning aggregation management is warranted that provides full protection from fishing to enhance population persistence. The findings also highlight the need for substantially greater enforcement and long-term fisheries monitoring under a comprehensive regional management strategy.     

Age, growth and reproduction of the humpback red snapper Lutjanus gibbus off Ishigaki Island, Okinawa

The humpback red snapper Lutjanus gibbus (Lutjanidae) is an important species for fisheries in the Kagoshima and Okinawan region of Japan. The present study estimated the age, growth and reproduction of this lutjanid species in the waters around Ishigaki Island, southern part of Okinawa. An opaque zone was formed on the otolith every year, and this formation correlated with their spawning season; these zones were identified as annual rings. Maximum ages of 21 and 24 years were observed for males and females, respectively. The von Bertalanffy growth parameters clarifying the age–fork length relationship were as follows: L _∞ = 390.5 mm, K = 0.210 year⁻¹ and t ₀ = −1.88 year for males, and L _∞ = 303.4, K = 0.256 year⁻¹ and t ₀ = −3.05 year for females. The main spawning season was estimated as between May and October, since greater values of gonadosomatic index for females as well as maturation oocytes and/or postovulatory follicles were observed during those six months.     

Isolation and characterization of microsatellites in lane snapper (Lutjanus synagris), mutton snapper (Lutjanus analis), and yellowtail snapper (Ocyurus chrysurus)

Polymerase chain reaction primer pairs for a total of 25 nuclear‐encoded microsatellites (loci) were developed from genomic DNA libraries of lane snapper (Lutjanus synagris), mutton snapper (Lutjanus analis), and yellowtail snapper (Ocyurus chrysurus). The microsatellites include 24 perfect (21 dinucleotide and three trinucleotide) and one imperfect (combination tetranucleotide/tetranucleotide) repeat motifs. A total of 32 individuals of each species were assayed for allelic variation at all 25 microsatellites; reliable amplification products were generated for lane snapper (25 loci), mutton snapper (21 loci), and yellowtail snapper (24 loci). Significant deviations from Hardy–Weinberg expectations, following Bonferroni corrections, were found for one microsatellite in lane and yellowtail snappers, and for three microsatellites in mutton snapper. All pairwise comparisons of microsatellites (all three species) did not deviate significantly from genotypic equilibrium.     

Age and growth of Lutjanus kasmira (Forskål) in Hawaiian waters

The growth of Hawaiian taape, Lutjanus kasmira , was studied by examining otoliths and by analysing length-frequency distribution. Annual hyaline and opaque markings were visible in whole mounts of sagittae, which were verified by enumeration of daily increments with a scanning electron microscope (SEM) and through marginal increment analysis. The von Bertalanffy growth curve was fitted to the data, resulting in: where t. l . is total length (cm) and t is age (years). SEM observations revealed that the slowgrowth hyaline zones were composed of daily increments too small (0.4–0.8 μm) to be resolved optically. Thus, age estimates derived by numerically integrating otolith growth rate data obtained with a light microscope showed a negative bias, resulting in overestimation of growth rates. Parameter estimates obtained from three different types of length-frequency analysis were also unstable. This was due, at least in part, to differences in the size composition of fish sampled with different fishing gears and from different depths.
The growth rate registered in Hawaii falls within the reported growth coefficients of lutjanids, whereas it is one of the highest in the Pacific and clearly higher than a deep-water lutjanid species growth in Hawaii. Probably, this high growth rate may have been enhanced by the relative lack of competitors in the depauperate Hawaiian marine fish community.     

Expression and activity of trypsin and pepsin during larval development of the spotted rose snapper Lutjanus guttatus

The present study aimed to describe and understand the development of the digestive system in spotted rose snapper (Lutjanus guttatus) larvae from hatching to 40 days post-hatch (dph). The mouth opened between 2 and 3 dph, at that moment the digestive tract was barely differentiated into the anterior and posterior intestine, although the liver and pancreas were already present. Gastric glands were observed until 20 dph, followed by the differentiation of the stomach between 20 and 25 dph. Trypsinogen expression and trypsin activity were detected at hatching, increasing concomitantly to larval development and the change in the type of food. Maximum levels of trypsinogen expression were observed at 25 dph, when animals were fed with Artemia nauplii, and maximum trypsin activity was detected at 35 dph, when larvae were fed with an artificial diet. On the other hand, pepsinogen gene expression was detected at 18 dph, two days before pepsin enzymatic activity and appearance of gastric glands. Maximum pepsin activity was also observed at 35 dph. These results suggest that in this species weaning could be initiated at an earlier age than is currently practiced (between 28 and 30 dph), since larvae of spotted rose snapper develop a functional stomach between days 20 and 25 post-hatch.     

Prey selection by age-0 walleye pollock, Theragra chalcogramma, in nearshore waters of the Gulf of Alaska

Juvenile walleye pollock, Theragra chalcogramma, is the dominant forage fish on the continental shelf of the Gulf of Alaska, yet little is known about the feeding habits of this important interval of pollock life history. The taxonomic composition and size of prey found in the stomachs of age-0 juveniles collected at three nearshore locations in the Gulf of Alaska in September 1990 were compared to the composition and size of zooplankton collected in concurrent plankton tows. The maximum length of prey consumed increased dramatically over the length range of pollock examined (58–110 mm) from approximately 7 mm to 30 mm, due mainly to the consumption of large euphausiids and chaetognaths by the bigger individuals. The maximum width of prey changed little over this size range although there was a general increase in prey width with increasing predator size. The minimum prey length and width did not change with increasing fish size. Juvenile pollock generally selected the larger prey sizes relative to what was available. Juvenile pollock showed a marked preference for adult euphausiids and decapod larvae and an avoidance of copepods and chaetognaths relative to the numbers collected in net tows. These results are discussed relative to the feeding ecology of these juvenile fishes. This revised version was published online in July 2006 with corrections to the Cover Date.     

Reproductive activity in the checkered snapper, Lutjanus decussatus, off Ishigaki Island, Okinawa

The checkered snapper, Lutjanus decussatus, is an important species for fisheries in the Okinawan region. This study estimated the reproduction of this lutjanid species in the waters around Ishigaki Island. The main spawning season was estimated to be between June and October, since oocytes at the maturation stage and/or postovulatory follicles were found during the study period. In the main spawning season, high gonadosomatic index values were found around the time of the last quarter moon for each month from June to September. It is suggested that L. decussatus is a lunar-synchronized spawner off Ishigaki Island.     

Multiplex genotyping of novel tetranucleotide microsatellites from a marine foodfish species crimson red snapper (Lutjanus erythropterus)

Crimson red snapper (Lutjanus erythropterus) is an important marine foodfish species in Asia with great potentials for aquaculture. We isolated nine polymorphic microsatellites, among which eight were tetranucleotide repeats, and one was CA‐microsatellite. The average allele number present in 48 individuals was 11.1/locus, ranging from three to 33. The expected heterozygosity ranged from 0.49 to 0.97 with an average of 0.74. Six of the nine markers conformed to the Hardy–Weinberg expectations. No pairwise markers showed the possibility of linkage. Protocols for two multiplex polymerase chain reactions (PCRs), each amplifying two and seven markers, respectively, were presented. The developed microsatellites and optimized multiplex PCRs will be useful for studying population structure of wild stocks and parentage assignment for cultured populations.     

The potential for intracohort cannibalism in age-0 walleye pollock,Theragra chalcogramma,as determined under laboratory conditions

Synopsis In laboratory experiments, we tested the capability of larger age-0 walleye pollock to consume smaller members of their cohort. In separate aquaria, 81 pairs of juveniles covering a wide range of size differences (total lengths differing by 12 to 61 mm) were held and monitored over a 4 day period. Complete consumption, in which a smaller fish was swallowed whole by a larger fish, occurred 11% of the time. In 36% of the pairs, attacks by the larger fish resulted in mortality of the smaller fish. The mouth width:body depth ratio between the larger and smaller fish of a pair differed significantly depending on whether the smaller fish survived, was killed but not consumed, or was ingested whole by the larger fish. Cannibalistic individuals could consume fish close to the maximum size physically possible under gape limitation; at this size the length of the cannibal was approximately 1.7 times the length of the prey. Length-frequency distributions of age-0 pollock in field concentrations suggested that, at least in some geographical areas, potential cannibals and prey commonly co-occur. Unsuccessful predatory attacks by larger individuals may have additional detrimental effects on smaller pollock in natural populations.     

Vibrios of the spotted rose snapper Lutjanus guttatus Steindachner, 1869 from northwestern Mexico

AIM: To characterize and identify vibrios present in wild and cultured juvenile snappers (Lutjanus guttatus) in northwestern Mexico. METHODS AND RESULTS: Spotted rose snapper juveniles were collected at four localities in northwestern Mexico. Bacteria were isolated from external lesions, kidney, liver, and spleen from cultured and wild caught organisms. In total, 280 isolates were obtained and fingerprinted with rep-PCR (GTG5). Nearly 93.2% of the strains belonged to the Vibrionaceae family. Species and genera identified were Photobacterium damselae subsp. damselae (76 strains), Photobacterium leiognathi (13), Vibrio sp. (24), Vibrio alginolyticus (12), Vibrio campbellii (19), Vibrio fortis (9), Vibrio harveyi (49), Vibrio ichthyoenteri (4), Vibrio mediterranei (4), Vibrio parahaemolyticus (1), Vibrio ponticus (2), Vibrio rotiferianus (22), and four potential new species. Conclusions: A wide diversity of vibrios was found in the external lesions and internal organs of both wild and cultured spotted rose snapper juveniles. In total, 12 species of vibrios and four potential new species were identified. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study on the vibrios present in the spotted rose snapper and therefore might serve as a basis for future studies and diagnosis.     

Validation of annual periodicity in otoliths of red snapper, <Emphasis Type="Italic">Lutjanus campechanus</Emphasis>

The periodicity of otolith growth increments (opaque and translucent zones) from adult red snapper (Lutjanus campechanus) was examined through a mark and recapture study (2005–2010), and laboratory holding of hatchery reared red snapper over a 2 year period (2002–2004). Wild red snapper (n = 295) were caught hook-and-line, marked with anchor tags, injected with oxytetracycline dihydrate (OTC), and released in the Gulf of Mexico 15–40 km south of Dauphin Island, Alabama. Marked fish were recaptured up to 2.8 years after release (n = 35) and sagittal otoliths were dissected, sectioned and examined under white and blue-violet light. The number of opaque growth zones past the OTC mark was compared to time at liberty for each fish and supported an annual periodicity of growth increment formation. Also, most (87%) of the hatchery reared fish showed two opaque zones that supported an annual increment formation rate. However, an unusual timing of opaque zone formation was shown for mark-recaptured fish. Based on known timing of OTC marking, otoliths from mark-recapture fish showed opaque zone formation from late summer (August) to early winter (December). This fall formation of opaque zones is in contrast to previous studies and its timing may relate to the end of spawning for this species.     

Systemic infection of Kudoa lutjanus n. sp. (Myxozoa: Myxosporea) in red snapper Lutjanus erythropterus from Taiwan

A new species of Kudoa lutjanus n. sp. (Myxosporea) is described from the brain and internal organs of cultured red snapper Lutjanus erythropterus from Taiwan. The fish, 260 to 390 g in weight, exhibited anorexia and poor appetite and swam in the surface water during outbreaks. Cumulative mortality was about 1% during a period of 3 wk. The red snapper exhibited numerous creamy-white pseudocysts, 0.003 to 0.65 cm (n = 100) in diameter, in the eye, swim bladder, muscle and other internal organs, but especially in the brain. The number of pseudocysts per infected fish was not correlated with fish size or condition. Mature spores were quadrate in apical view and suboval in side view, measuring 8.2 +/- 0.59 microm in width and 7.3 +/- 0.53 microm in length. The 4 valves were equal in size, each with 1 polar capsule. Polar capsules were pyriform in shape, measuring 3.62 +/- 0.49 microm in length and 2.2 +/- 0.49 microm in width. Mild inflammatory responses or liquefaction of host tissue were associated with K. lutjanus n. sp. infection. The junction of shell valves appeared as overlapping, straight lines. The polar filament formed 2 to 3 coils. A general PCR (polymerase chain reaction) primer for Kudoa amplified the small subunit (SSU) rDNA sequences, and the amplified gene was sequenced. It was evident from the phylogenetic tree that the 3 strains tested, AOD93020M, AOD93028M and AOD93028B, were identical and belonged to the Kudoa SS rRNA subgroup. The evolutionary tree showed that these strains form a unique clade, at a distance from other Kudoa species and myxosporeans. The spore's morphological and ultrastructural characteristics, as well as the SS rDNA properties of the isolates, were also essentially identical and served to distinguish them from representative Kudoa. It is, therefore, proposed that the strains isolated from the diseased red snapper be assigned to a new species.     

Construction of a fusion flagellin complex and evaluation of the protective immunity of it in red snapper (Lutjanus sanguineus)

Aims: The main aims of this study were to construct a bivalent subunit vaccine containing flagellin flaA gene and flagellin flaB gene from Vibrio alginolyticus strain HY9901 and to explore the potential application of the fusion protein FlaA‐(G₄S)₃‐FlaB as a vaccine candidate for red snapper (Lutjanus sanguineus). Methods and Results: Flagellin gene flaA and flaB of V. alginolyticus were linked by gene SOEing (gene splicing by overlap extension) technology. The expression of the fusion gene flaA‐(G₄S)₃‐flaB in Escherichia coli BL21(DE3) was confirmed by SDS‐PAGE. Western blot analysis showed that the fusion protein FlaA‐(G₄S)₃‐FlaB, which was purified by affinity chromatography on Ni‐NTA resin, had positive reaction with mouse anti‐FlaA serum and mouse anti‐FlaB serum, respectively. The immunoprotection of FlaA‐(G₄S)₃‐FlaB as a bivalent subunit vaccine was investigated in red snapper model by enzyme‐linked immunosorbent assay (ELISA) and challenge test. Red snapper vaccinated with FlaA‐(G₄S)₃‐FlaB produced specific antibodies and were highly resistant to infection by virulent V. alginolyticus. Conclusions: The fusion gene flaA‐(G₄S)₃‐flaB from V. alginolyticus strain HY9901 was cloned by gene SOEing and was expressed in E. coli. This fusion protein FlaA‐(G₄S)₃‐FlaB is a good protective antigen of V. alginolyticus and should be considered as an effective vaccine candidate against infection by V. alginolyticus in red snapper. Significance and Impact of the Study: Two flagellin genes, flaA and flaB, which are independent in structure and function, were first linked together by gene SOEing technology. The finding that red snapper did adequately respond to the fusion protein FlaA‐(G₄S)₃‐FlaB injection made it a promising candidate for vaccine treatment. To develop effective vaccine candidates against V. alginolyticus, more attention should be given to these immunogenic flagellins.     

Predation by Moses perch, Lutjanus russelli, and blue-spotted trevally, Caranx bucculentus, on juvenile brown tiger prawn, Penaeus esculentus: effects of habitat structure and time of day

The effects of habitat structure and time of day on predation success of Moses perch, Lutjanus russelli , and blue-spotted trevally, Caranx bucculentus , feeding on juvenile brown tiger prawn, Penaeus esculentus , were tested in the laboratory. Our experiments demonstrated that both softsubstratum, in which prawns can burrow, and seagrass habitats reduce predation rates by fish during daytime when compared to hard-substratum habitats. However, the protection offered by burrowing in a soft substratum during daytime disappears at night when prawns become active and are more available to fish. Seagrass structure offers the same protection during both night and day. This is attributed to the structural complexity of the seagrass habitat, as well as the behaviour and disruptive coloration of the prawns. The results suggest that fish predation on juvenile P. esculentus may not be very important in seagrass nurseries but could be very high in other habitats.