Comparative morphology of the pectoral fin spine of the Persian sturgeon Acipenser persicus,the Russian sturgeon Acipenser gueldenstaedtii,and the Starry sturgeon Acipenser stellatus in Iranian waters of the Caspian Sea

The morphological characteristics of the pectoral fin spine were compared in three species of sturgeon, the Persian sturgeon (Acipenser persicus), the Russian sturgeon (Acipenser gueldenstaedtii), and the Starry sturgeon (Acipenser stellatus), all sampled from the Caspian Sea. On the basis of morphological characters of the pectoral fin spine, 62.2% of the individuals were correctly classified into separate groups. The cluster analysis also divided the three species into two major subgroups. Acipenser persicus and A. gueldenstaedtii were grouped together, suggesting a similar evolutionary basis. Significant morphological heterogeneity in pectoral fin spine characteristics was observed among the three sturgeon species. Principal component analysis identified the largest differences were in the pectoral fin spine size and the angle between distal pectoral fin spine and the horizontal line (A°). The first and second principal components (PC1 and PC2) of all observations accounted for 64.19% and 14.33% of the total variation, respectively. The combination of all analyses showed the relevance of applying pectoral fin spine shape for interspecific distinction of the three species of sturgeons.     

Application of enriched <Superscript>137</Superscript>Ba tracer to mark juvenile Persian sturgeon (<Emphasis Type="Italic">Acipenser persicus</Emphasis>)

The present study evaluates the variations of ¹³⁷Ba abundance in pectoral fin spine of 1-month-old juvenile Persian sturgeon (Acipenser persicus) upon marking using the stable isotope approach. The marking of the fish was achieved by incorporation of ¹³⁷Ba²⁺ in the calcified lattice of the pectoral fin spine through substitution with structural Ca²⁺. This process was carried out by rearing juveniles in treatment tanks containing elevated concentrations of ¹³⁷Ba for 1, 3 and 5 days. The marked fish were then retained in natural abundance fresh and brackish waters, to evaluate the trend of exchange of ¹³⁷Ba from the fin spines. The abundance of ¹³⁷Ba in fin spines during marking and post-marking experiments were detected by inductively coupled plasma mass spectrometry (ICP-MS). The results showed that a significant isotope mark can be obtained with no mortality and 100% marking rate on the first day of exposure to the isotope. The marked juveniles maintained their isotopic signature for at least 25 days. Statistical analysis of the obtained ¹³⁸Ba/¹³⁷Ba ratios demonstrated that the successful incorporation of ¹³⁷Ba²⁺ in pectoral fin spines provides an effective marking method for Persian sturgeon restocking programs.     

Age structure of juvenile Amur sturgeon Acipenser schrenckii and kaluga Huso dauricus in the Fuyuan reach of the Amur River,Northeast China

Amur sturgeon Acipenser schrenckiii Brandt 1869 and kaluga Huso dauricus (Georgi 1775) are critically endangered species with populations showing significant decline from historical levels due to overexploitation, yet little is known about their population structure. Adults are not often captured in the Fuyuan reach of the Amur River, Heilongjiang Province, Northeast China, and the government prioritizes juvenile sturgeon management. This study was conducted to determine the age and length/weight relationships of juvenile Amur sturgeon and kaluga in the Fuyuan reach of the Amur River. We estimated age using pectoral fin spine sections obtained from 65 juvenile Amur sturgeon and 50 juvenile kaluga. We compared the age estimates from two readers, and found 100% between‐reader agreement in 67.7% of the Amur sturgeon and 64.0% of the kaluga. The majority of differences in estimated age were within 1 year. Length/weight relationships (LWR) were calculated, and the LWR of the Amur sturgeon and kaluga were W = 0.0025L3.106 (r² = 0.966）and W = 0.0022L3.175 (r² = 0.989), respectively. Our study provides the age structure and LWR in juveniles of two sturgeon species.     

Using energy dispersive x-ray fluorescence microchemistry to infer migratory life history of Atlantic sturgeon

Atlantic sturgeon migrate between ocean and freshwater habitats to spawn, and juveniles spend several years in fresh/brackish water before returning to the ocean. Because strontium/calcium (Sr/Ca) ratios are diagnostic for freshwater and marine environments, we examined the utility of energy-dispersive x-ray fluorescence (EDXRF) to quantify Sr/Ca ratios of Atlantic sturgeon pectoral fin spines. Atlantic sturgeon spines from wild adults and experimental juveniles were analyzed along a linear transect from the primordium to the outermost point. To verify the technique hatchery juvenile Atlantic sturgeon were held in experimental tanks at <0.5, 13?C15, or 33?C35?? and sampled after 5?months. Sr/Ca ratios of experimental hatchery fish increased with salinity, and Sr/Ca ratios in wild adults varied predictably along the measurement transect. However, the ratio decreased in the outermost region of the spine in mature fish collected during a return to freshwater for spawning. Therefore EDXRF is a useful tool to track individual movements of Atlantic sturgeons and other diadromous fish.     

Natural stranding of Atlantic sturgeon (Acipenser oxyrinchus Mitchill, 1815) in Scot's Bay,Bay of Fundy,Nova Scotia,from populations of concern in the United States and Canada

Natural mortality of Atlantic sturgeon (Acipenser oxyrinchus) has been determined to be low (M = 0.07). Reported herein is the mortality by beach stranding of 11 Atlantic sturgeon in Scot's Bay, part of the inner Bay of Fundy in Nova Scotia, Canada on 22 June 2014. Genetic analyses, histological analysis and age determination were performed to determine origin, maturity stage and age of the stranded Atlantic sturgeon. Microsatellite and mitochondrial DNA analyses indicated that four of the Atlantic sturgeon (2 males and 2 females) were from the Saint John River, NB population, which was designated as threatened by the Committee on the Status of Endangered Wildlife in Canada. Seven Atlantic sturgeon (1 male, 5 females, 1 unknown) were from the Kennebec River, Maine population, that was listed as threatened under the Endangered Species Act in the U. S. Ageing of A. oxyrinchus Atlantic sturgeon by pectoral fin spine analysis determined that the mean age of the individuals from the Saint John River (x? = 24.25 years, SD = 5.0) and the Kennebec River (x? = 22.7 years, SD = 3.5) were not significantly different. This is the first report of a stranding event of Atlantic sturgeon, and describes a source of natural mortality affecting populations of concern in both Canada and the U. S.     

Growth and morphological development of laboratory-reared larval and juvenile Pangasianodon hypophthalmus

The morphological development, including the fins, body proportions and pigmentation, of laboratory-reared larval and juvenile Pangasianodon hypophthalmus was described and their behavioral features were observed under rearing conditions. Body lengths (BL) of larvae and juveniles were 3.0 ± 0.2 (mean ± SD) mm just after hatching, and 12.9 ± 1.1 mm on day 13, reaching 23.4 ± 1.8 mm on day 25 after hatching. Aggregate fin ray numbers (for caudal fin, principal soft ray number) attained their full complements in specimens larger than 12.8 mm BL. Notochord flexion began in yolksac larvae on day 0 (10.5 h after hatching), with teeth buds and barbels appearing with jaw formation in yolksac flexion larvae on day 1. Melanophores on the body increased with growth, with a broad vertical band forming on the lateral line and an oblique band extending from above the pectoral fin base towards the forepart of the anal fin during the postflexion larval and juvenile stages. Body proportions became relatively constant in juveniles, except for maxillary barbel length (MBL), which continued to decrease. Yolksac flexion larvae started feeding on day 2 with the onset of intense cannibalism. Yolks were completely absorbed by day 3, and cannibalism ended by day 6. Subsequently, fish displayed a schooling behavior with growth, preferring relatively dark areas during the juvenile stage.     

Developmental morphology of the cottid fish Pseudoblennius marmoratus

Embryonic, larval, and juvenile development of a Japanese cottid fish Pseudoblennius marmoratus is described from laboratory-reared specimens. Eggs of P. marmoratus resembled those of two congeners, Pseudoblennius cottoides and Pseudoblennius percoides, but differed in their smaller diameter and yolk color. Although the larvae and juveniles of P. marmoratus were also similar to them in general morphology, the former differed in the lengths of newly hatched larvae, pigmentation patterns, number of pectoral fin rays, and dorsal fin spine elongation.     

Larvae and juveniles of the plunderfishes <Emphasis Type="Italic">Artedidraco shackletoni</Emphasis> and <Emphasis Type="Italic">A.</Emphasis><Emphasis Type="Italic">skottsbergi</Emphasis> (Notothenioidei,Artedidraconidae) from the Indian sector of the Southern Ocean

Early life stages of Artedidraco skottsbergi and A. shackletoni were collected off Adélie Land. The morphology and pigmentation pattern of nine larvae and juveniles of A. skottsbergi between 17.2 and 21.4 mm in standard length (SL), and of two juveniles of A. shackletoni measuring 25.1 mm SL were described. A. skottsbergi was characterized by a heavily pigmented body, except for the caudal peduncle, with distinctively dense pigmentation on the ventrolateral half of the body and caudal section (17.2–17.9 mm SL). Furthermore, they had no pigmentation on the pectoral fin base until they attained 21.4 mm SL. Juvenile A. shackletoni had a heavily pigmented body except for the ventral side of the abdomen and the anal fin base. The proximal part of the dorsal fin and most of the anal fin were covered with melanophores. Although knowledge of larval and juvenile Artedidraco species is limited, the distribution of melanophores on the fins, pectoral fin base and caudal peduncle at each developmental stage may be useful for species identification.     

Optimal stocking density for beluga,Huso huso,and ship sturgeon,Acipenser nudiventris during the grow‐out phase

The influence of three different initial stocking densities (SD) in flowthrough systems was evaluated on growth performance and feed utilizaition in beluga, Huso huso, and ship sturgeon, Acipenser nudiventris, juveniles in three different grow‐out phases for 228 days. In each grow‐out phase, fish were randomly distributed in 18 concrete square tanks (2.0 × 1.0 × 1.2 m³; 2 m³ of volume) according to the experimental SD. At the first phase, both fish species were subjected to three SD including 1.5, 3 and 6 kg/m² for 60 days. In the second phase, fish were submitted to three SD including 3, 6 and 9 kg/m², whereas in the third phase, beluga were stocked at 6, 9 and 12 kg/m² and ship sturgeon were stocked at 6, 8 and 10 kg/m² and each phase lasted for 12 weeks. In both species, the growth performance and feed intake (FI) significantly decreased with increasing SD at the end of the first phase (p < 0.05). In the second phase, growth performance and FI in beluga decreased with increasing SD, whereas in ship sturgeon neither growth nor FI were affected by SD. Interestingly, the growth performance and feed utilization in both species were not decreased with increasing SD in the third phase indicating adaptability of these species to high stocking density during grow‐out period. According to the result of this study, the appropriate initial SD for beluga within the range of 100–500, 500–2,000 and 1,500–3,000 g were at 1.5, 6 and 12 kg/m², respectively in an open flow‐throw system. Regarding to ship sturgeon, initial SD at 1.5 and 10 kg/m²recommended for fish within the range of 100–300 and 300–1,200 g, respectively in an open flow‐throw system.     

A new genus and species of prickleback (Perciformes: Stichaeidae) from Japan

A stichaeid fish, Xenolumpenus longipterus gen. et sp. nov., is described on the basis of 2 specimens (107.1–114.9 mm in standard length) collected from 167 to 300 m in the northern Sea of Japan off southern Hokkaido, Japan. Xenolumpenus is unique among all known genera of the subfamily Lumpeninae in having all pectoral, pelvic, and anal fin rays elongate and unbranched with fin membranes well-incised. Xenolumpenus longipterus can be further distinguished from all species of the subfamily in having the following combination of characters: dorsal fin XLVI–XLVIII; anal fin II, 28–29; pectoral fin 11; large black blotches on pectoral fin; and black ocellus on caudal fin.     

Saddleback syndrome in yellowfin bream [Acanthopagrus australis (Günther, 1859)] in Moreton Bay,Australia: its form,occurrence, association with other abnormalities and cause

The aim of this study was to determine if saddleback syndrome (SBS) in a wild population of yellowfin bream (Acanthopagrus australis) was the result of a developmental defect or caused by physical injury. Information was collected in 2012 on the incidence of SBS and other abnormalities in this species in Moreton Bay, Australia. Abnormalities in adult fish (>250 mm Total Length, TL) with SBS (n = 47) were compared with those without SBS (n = 30). A sample of juvenile fish (n = 404) was checked for the presence of SBS. The results show that scale loss, scale pattern misalignment, lateral line fracture and pectoral fin abnormality were closely associated with SBS. SBS was uncommon (<2%) in juveniles <70 mm TL, but common (>12%) in the larger juveniles (70–215 mm TL). These results, together with the findings that scale loss associated with SBS in adult fish occurred in the range 80–245 mm back‐calculated TL, indicate that SBS and the related abnormalities in yellowfin bream are a result of physical injuries to larger juveniles (>70 mm TL). The reduction in the incidence of SBS from approximately 12% in the larger juveniles to 5% in adults is evidence of mortality associated with SBS.     

Application of non‐lethal stable isotope analysis to assess feeding patterns of juvenile pallid sturgeon Scaphirhynchus albus: a comparison of tissue types and sample preservation methods

Traditional techniques for stable isotope analysis (SIA) generally require sacrificing animals to collect tissue samples; this can be problematic when studying diets of endangered species such as the pallid sturgeon Scaphirhynchus albus. Our objectives were to (i) determine if pectoral fin tissue (non‐lethal) could be a substitute for muscle tissue (lethal) in SIA of juvenile pallid sturgeon, and (ii) evaluate the influence of preservation techniques on stable isotope values. In the laboratory, individual juvenile pallid sturgeon were held for up to 186 day and fed chironomids, fish, or a commercially available pellet diet. Significant, positive relationships (r² ≥ 0.8) were observed between fin and muscle tissues for both δ¹⁵N and δ¹³C; in all samples isotopes were enriched in fins compared to muscle tissue. Chironomid and fish based diets of juvenile pallid sturgeon were distinguishable for fast growing fish (0.3 mm day^?1) using stable δ¹⁵N and δ¹³C isotopes. Frozen and preserved fin tissue δ¹⁵N isotopes were strongly related (r² = 0.89) but δ¹³C isotopes were weakly related (r² = 0.16). Therefore, freezing is recommended for preservation of fin clips to avoid the confounding effect of enrichment by ethanol. This study demonstrates the utility of a non‐lethal technique to assess time integrated food habits of juvenile pallid sturgeon and should be applicable to other threatened or endangered species.     

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.     

Trace element and strontium isotopic analysis of Gulf Sturgeon fin rays to assess habitat use

Trace element and ⁸⁷Sr/⁸⁶Sr isotope analyses of fish pectoral fin rays offer non-destructive methods for determining habitat use. In this study, water and fin ray samples were analyzed for Gulf Sturgeon Acipenser oxyrinchus desotoi from the Choctawhatchee River Basin (FL and AL, USA) and compared with reference samples from Atlantic Sturgeon A. o. oxyrinchus held at controlled salinities (0, 10, 33 ppt). Samples were analyzed using inductively coupled plasma mass spectrometry, with a multi-collector for ⁸⁷Sr/⁸⁶Sr. In water, Sr, Ba, Mn and Zn differed between freshwater and saline habitats, with increases in Sr and decreases in Ba, Mn and Zn. ⁸⁷Sr/⁸⁶Sr decreased upstream to downstream with lowest values in saline habitats. In the reference study, water trace element concentrations and ⁸⁷Sr/⁸⁶Sr corresponded to those in pectoral fin rays. ⁸⁷Sr/⁸⁶Sr was higher in pectoral fin ray than water, due to influence of diet, which differed with salinity. In wild fish, trace elements in pectoral fin rays indicated freshwater emigration to saline habitats primarily occurred in the second to third growth zone with some heterogeneity in the population (4% <0.3 years, 39% 0.5–1.3 years, 39% 1.5–2.3 years, 17% 2.5–3.3 years). Analyses of ⁸⁷Sr/⁸⁶Sr indicated initial locations of Gulf Sturgeon were in the middle river, with few fish in the upper or lower river. Most (74%) juvenile Gulf Sturgeon utilized more than one river region prior to freshwater emigration and 48% moved upstream temporarily based on increased ⁸⁷Sr/⁸⁶Sr. After initial freshwater emigration, fish utilized lower-river to saline habitats. Collectively, these studies demonstrate the usefulness of trace element and ⁸⁷Sr/⁸⁶Sr analyses in sturgeon pectoral fin rays.     

The effect of feeding strategies and body weight on growth performance and hematological parameters of Siberian sturgeon (Acipenser baerii,Brandt 1869): Preliminary results

The purpose of present study was to investigate the growth performance and hematological parameters of Siberian sturgeon Acipenser baerii in three feeding strategies (satiation feeding, restricted feeding and starvation). We considered two body weights 465.75 ± 11.18 g and 250.40 ± 12 g for large fish and small fish, respectively. In a 45‐day experiment, eighteen fiberglass tanks were used for six triplicate treatments. In restricted feeding strategy, the fish were fed to 50% of satiation and starved treatments were an absolute feed deprivation throughout the experiment. At the end of 45‐day period, the hematological parameters were measured. The reduction of weight, condition factor and daily growth rate in the smaller fish was dramatically higher than the larger fish. Feed deprivation increased the rate of weight loss. Specific growth rate were negative in the large and small fish of starved treatments. The hematological results revealed no significant differences in except for the number of monocytes in larger fish. Large satiated fish showed the highest number of monocytes. In general, these strategies (restriction and deprivation) did not have any negative impacts on the hematological parameter in both sizes but respect to fish body weight, difference in total feed input between satiated and restricted treatments changed growth performance. It seems that restricted feeding (50% of satiation) in large fish was enough to achieve optimal growth while the amount of feed provided for small fish was not enough. Therefore; we can conclude that the restricted feeding is an effective strategy in rearing sturgeon at higher weight when the rearing condition is unsuitable.     

Effect of temperature on fatty acid composition and development of unfed Siberian sturgeon (A. baerii) larvae

The fatty acid metabolism in fish is influenced by various factors, including fish species, water temperature, water environment and diet supply. The aim of present work is to investigate the fatty acid composition of yolk‐stage Siberian sturgeon larvae reared at three different temperatures. Fertilized Siberian sturgeon eggs were transferred to the Lodi Aquaculture Research Center of the University of Milan, divided in three aquaria, each containing three incubators and incubated at 16°C. After hatching the temperature was switched to 16, 19 and 22°C. Larvae sampling was performed at the end of yolk sac reabsorption. No feed was dispensed during the trial. Eggs and larvae were weighed and fatty acid profile was determined by GC‐FID analysis after lipid extraction by chloroform/methanol mixture and fatty acid transesterification by methanolic hydrogen chloride. The fertilized eggs had a weight of 23.27 mg and a lipid content of 2.67 mg/egg. At hatching, the weight was 12.2 (0.17 SD) mg and lipid content 1.9 (0.6 SD) mg/larva. At the end of the trial, larvae mean weight was 33.6 (3.6 SD), 34.7 (1.8 SD) and 36.9 (1.1 SD) mg, while lipid content was 2.0 (0.3 SD), 2.1 (0.3 SD) and 2.0 (0.2 SD) mg for larvae reared at 16, 19 and 22°C respectively, without statistically significant difference. Larvae subjected to the highest water temperature showed a faster yolk‐sac absorption. No differences were found across temperatures regarding survival rates and regarding ontogenic development. The fatty acid composition of larvae was affected by the temperature. Larvae reared at 16°C had the lowest amount of saturated fatty acids, mainly due to a lower palmitic acid content, that was offset by a higher level of linolenic and linoleic acid, if compared with larvae reared at 19°C and 22°C. The study suggests that at a lower temperature sturgeon spare unsaturated fatty acid consuming preferably saturated fatty acids, increasing our knowledge of the fatty acid metabolism in this species.     

Characteristics of lake sturgeon Acipenser fulvescens Rafinesque, 1817 in a tributary of Lake Michigan,USA: Status of the Muskegon River population

The overall goal of this study was to characterize the age, growth, condition, and total catch of lake sturgeon Acipenser fulvescens in a remnant population associated with a Lake Michigan, USA tributary. Lake sturgeon were captured (2008–2013) using large‐mesh (25.4 and 30.5 cm) and small‐mesh (6.4 and 7.6 cm) gill netting in Muskegon Lake (which connects the Muskegon River to Lake Michigan), and adults were captured with boat electrofishing in the Muskegon River. A total of 268 unique lake sturgeon (24.8–191.0 cm total length; <0.1–59.5 kg weight) were captured. Of these, 180 fish were aged using pectoral fin rays, representing 27 age cohorts and a mean age of 7.6 years. The weight–length relationship for lake sturgeon was log₁₀ (W) = 3.446·log₁₀ (L) ? 6.163 and the von Bertalanffy growth model was L = 180.719 [1?e^{?0.093(t + 0.902)}], where W was wet weight (kg), L was total length (cm), and t was age (years). Mean growth rate of juveniles (ages 3–6) recaptured in successive years was 8.6 cm/year and 558 g/year. Annual catch of adults during the spawning migration suggested that the number of spawners each year was low (i.e., probably <50 individuals in most years). Natural reproduction appeared to be occurring given the catch of juvenile lake sturgeon in Muskegon Lake. However, recovery of this remnant population is uncertain given the population age structure and low rate of adult recruitment during the study.     

Diet of farm‐escaped sturgeon in the Yangtze River

The diet of farm‐escaped sturgeon accidentally introduced into the Yangtze River ecosystem was investigated from samples collected over 10 days. The fish had consumed adequate quantities of natural food, with prey type related to fish body size. The fish were categorized according to their primary dietary component: demersal fish were most common prey of kaluga Huso dauricus and H. dauricus × Acipenser schrenckii hybrids of total length 120.3–188.7 cm. Shrimp Macrobrachium nipponensis made up the major portion of the diet of H. dauricus × A. schrenckii and Acipenser baerii × A. schrenckii of total length 91.1–106.8 cm. Gammarid amphipods were consumed by A. baerii × A. schrenckii of total length 35.0–81.2 cm. The body length of prey was proportional to the fork length of the sturgeon, Y = 0.19X‐9.46, R² = 0.997. Escaped sturgeon had travelled at least 898 km downstream from the point of escape in the Yangtze River and were feeding on native macrobenthos and demersal fish.     

<Emphasis Type="Italic">Rogadius mcgroutheri</Emphasis>, a new species of flathead (Teleostei: Platycephalidae) collected from eastern Australia and New Caledonia

A new platycephalid, Rogadius mcgroutheri, is described on the basis of the specimens collected from eastern Australia and New Caledonia. Rogadius mcgroutheri is distinguished from other congeners by 11 second dorsal fin rays usually, 4 or 6–8 unbranched lower pectoral fin rays, larger orbital diameter, usually single preocular spine lacking the accessory spines on the anterior base, short antrorse preopercular spine, tooth band on palatine narrow, with 2 irregular tooth rows, body with indistinct or somewhat distinct brown blotches, and caudal fin with dark brown spots and bands.