Precision of the age–length increments of three cyprinids: effects of fish number and sub‐sampling strategy

The effects of number of fish that are aged and scale sub‐sampling strategies on the precision of estimates of mean age–length increments from populations of Rutilus rutilus, Leuciscus leuciscus and Leuciscus cephalus were tested. Analyses used data derived from river fish communities in eastern England, U.K.. Regarding the number of fishes analysed in each age group, for each species and mean fork‐length increment at age, significant relationships were detected between sample size (n) and the coefficient of variation of the mean (Z) and mean length increment and measured variance (s²). This enabled calculation of the number of scales for producing a mean length increment at age according to . Outputs indicated that the number of scales requiring ageing increased substantially as precision increased, but with little variation between species per age category. Ageing between seven and 12 scales per age group would thus provide estimates at 10% precision. As the ages of fishes are not known in advance of scale ageing, the effect of scale sub‐sampling regime on precision was also tested using randomized strategies of 10 fish per 5 mm, five per 5 mm, three per 5 mm, 10 per 10 mm, five per 10 mm and three per 10 mm. These were applied to the datasets and the consequences of their reduction in the number of scales for precision were determined using . When compared to no sub‐sampling, three per 10 mm always significantly reduced data precision, whereas 10 per 5 mm never significantly reduced precision. These outputs can thus be applied to the design of fish sampling protocols where age and growth estimates are required, with the randomized sub‐sampling likely to be the most useful strategy.     

Developmental changes in oxygen consumption and hypoxia tolerance in the heat and hypoxia-adapted tabasco line of the Nile tilapia Oreochromis niloticus,with a survey of the metabolic literature for the genus Oreochromis

The genus Oreochromis is among the most popular of the tilapiine cichlid tribe for aquaculture. However, their temperature and hypoxia tolerance, if tested at all, is usually tested at temperatures of 20–25°C, rather than at the considerably higher temperatures of 30–35°C typical of tropical aquaculture. We hypothesized that both larvae and adults of the heat and hypoxia-adapted Tabasco-line of the Nile tilapia Oreochromis niloticus would be relatively hypoxia-tolerant. Oxygen consumption rate (), Q₁₀ and aquatic surface respiration (ASR) was measured using closed respirometry at 2 (c. 0.2 g), 30 (c. 2–5 g), 105 c. (10–15 g) and 240 (c. 250 g) days of development, at 25°C, 30°C and 35°C. at 30°C was inversely related to body mass: c. 90 μM O₂ g⁻¹/h in larvae down to c. 1 μM O₂ g⁻¹/h in young adults. Q₁₀ for was typical for fish over the range 25–35°C of 1.5–2.0. ASR was exhibited by 50% of the fish at pO₂ of 15–50 mmHg in a temperature-dependent fashion. However, the largest adults showed notable ASR only when pO₂ fell to below 10 mmHg. Remarkably, p_crit for was 12–17 mmHg at 25–30°C and still only 20–25 mmHg across development at 35°C. These values are among the lowest measured for teleost fishes. Noteworthy is that all fish maintain equilibrium, ventilated their gills and showed routine locomotor action for 10–20 min after ceased at near anoxia and when then returned to oxygenated waters, all fish survived, further indicating a remarkable hypoxic tolerance. Remarkably, data assembled for from >30 studies showed a > x2000 difference, which we attribute to calculation or conversion errors. Nonetheless, p_crit was very low for all Oreochromis sp. and lowest in the heat and hypoxia-adapted Tabasco line.     

Excess post‐hypoxic oxygen consumption in Atlantic cod Gadus morhua

Atlantic cod Gadus morhua experienced oxygen deficit () when exposed to oxygen levels below their critical level (c. 73% of p_crit) and subsequent excess post‐hypoxic oxygen consumption (C_EPHO) upon return to normoxic conditions, indicative of an oxygen debt. The mean ± s.e . C_EPHO: was 6·9 ± 1·5, suggesting that resorting to anaerobic energy production in severe hypoxia is energetically expensive.     

A new miniature species of the genus Triplophysa (Balitoridae: Nemacheilinae) from Yunnan, China

During a re-examination of museum specimens of Triplophysa species, some specimens that had been collected from the Jialonghe River in Yunnan Province, China, in April 1975, were identified as a new species. Triplophysa parvus n. sp. can be distinguished by the following combination of characters: dorsal fin rays 3, ; anal fin rays 3, ; pectoral fin rays 1, 11; scales absent; two saddle-like blotches with fuzzy borders cranial to the dorsal fin and four saddle-like blotches caudal to the dorsal fin; distal margin of the dorsal fin emarginate; pelvic fin reaching caudally almost to the anus; anus located immediately cranial to the origin of the anal fin; caudal fin forked; caudal chamber of air bladder reduced to a small free protuberance; head slightly laterally compressed, head deeper than wide at nape; length of caudal peduncle being 18.0–20.0% of standard length; depth of caudal peduncle being 7.8–8.4% of standard length; eye diameter 17.6–21.4% of head length; body depth being 60.7–70.2% of head length; caudal peduncle depth being 39.1–45.0% of caudal peduncle length; and body width at the base of caudal peduncle 59.0–68.0% of the body depth at the base of caudal peduncle. These characters allow a distinction from the similar species of T. nasobarbatula, T. nandanensis, and T. macromaculata.     

Steelhead trout Oncorhynchus mykiss metabolic rate is affected by dietary Aloe vera inclusion but not by mounting an immune response against formalin‐killed Aeromonas salmonicida

The oxygen consumption of two groups of 10° C acclimated steelhead trout Oncorhynchus mykiss was measured for 72 h after they were given a 100 µl kg^?1 intraperitoneal injection of formalin‐killed Aeromonas salmonicida (ASAL) or phosphate‐buffered saline (PBS). In addition, plasma cortisol levels were measured in fish from both groups prior to, and 1 and 3 h after, they were given a 30 s net stress. The first group was fed an unaltered commercial diet for 4 weeks, whereas the second group was fed the same diet but with 0·5% (5 g kg^?1) Aloe vera powder added; A. vera has potential as an immunostimulant for use in aquaculture, but its effects on basal and acute phase response (APR)‐related metabolic expenditures and stress physiology, are unknown. Injection of ASAL v. PBS had no measurable effect on the of O. mykiss indicating that the APR in this species is not associated with any net increase in energy expenditure. In contrast, incorporating 0·5% A. vera powder into the feed decreased routine metabolic rate by c. 8% in both injection groups and standard metabolic rate in the ASAL‐injected group (by c. 4 mg O₂ kg^?1 h^?1; 5%). Aloe vera fed fish had resting cortisol levels that were approximately half of those in fish on the commercial diet (c. 2·5 v. 5·0 ng ml^?1), but neither this difference nor those post‐stress reached statistical significance (P > 0·05).     

<Emphasis Type="Italic">Amblyceps improcerum</Emphasis>, a new sisoroid catfish from Kachin State,Myanmar (Teleostei: Siluriformes: Amblycipitidae)

A new species of amblycipitid catfish is here described from the Indawgyi Lake basin of the Irrawaddy River drainage in Kachin State, Myanmar as Amblyceps improcerum, new species. It can be distinguished from congeners in having a unique combination of the following characters: lower jaw longer than upper; head length 17.4–22.3% SL; head width 13.7–15.2% SL; head depth 9.0–11.7% SL; interorbital distance 31–39% HL; eye diameter 7–10% HL; 37–38 vertebrae; lateral line incomplete; predorsal length 25.5–30.7% SL; smooth posterior margin of pectoral spine; pectoral-fin length 13.5–16.8% SL; pelvic-fin length 9.6–13.4% SL; dorsal-to-adipose distance 25.2–28.7% SL; length of adipose-fin base 19.4–23.3% SL; adipose fin separate from dorsal procurrent caudal-fin rays; preanal length 62.1–66.9% SL; body depth at anus 9.8–12.8% SL; depth of caudal peduncle 10.1–12.6% SL; length of caudal peduncle 21.4–24.0% SL, post-adipose distance 15.8–17.8% SL; weakly-forked caudal fin with short broadly, rounded lobes (length of longest ray 1.3–1.5 times length of median rays); centrally projecting hooks on proximal lepidotrichia of median caudal-fin rays absent.     

Spatial pattern of distribution and reproductive strategy of vermiculate electric-rays Narcine vermiculatus

In the study, the authors evaluate the spatial distribution pattern of vermiculate electric-ray Narcine vermiculatus using geostatistical techniques to predict its spatial distribution and indicate its reproduction strategy. From January 2008 to December 2009, 3333 specimens of vermiculate electric-ray were caught. Total length (L_T), sex, maturity stage, catch location and depth were recorded for each specimen. The L_T of vermiculate electric-ray ranged from 6.7–24.6 cm. The authors estimate an irregular spatial structure, with a high-density patch ( 53 ind. ha⁻¹) located on the east coast, which concentrates 65.2% of the specimens. The high-density patch consists mainly of large juveniles (13.3–19.5 cm L_T), sub-adults (14.0–19.8 cm L_T) and young adults (14.7–21.3 cm L_T). Data indicate that adults migrate to the high-density patch to reproduce. Males reached maturity at 14.5 cm L_T, whereas females reached maturity at 19.3 cm L_T. Vitellogenesis in female vermiculate electric-ray begins in June; ovulation, mating, fertilization and gestation in October and birth begins in February. This indicates an annual cycle with vitellogenesis and consecutive gestation, in females synchronized in reproduction. Fecundity was 1–8 ( 4), and the sex ratio of embryos was 1:1. The birth occurred between February and April, with an average size at parturition of 6.3 cm L_T. Incidental capture of sub-adults and adults of N. vermiculatus by bottom trawls threatens the survival of this species.     

高原特有条鳅鱼类两新种在广西的发现及其动物地理学意义

描述了采自广西都安县红水河水系的条鳅亚科鱼类2个新种：丽纹云南鳅yhnnanilus pulcherrimussp．nov．在侧线长度、鳞片分布、鳍条数目、尾型、吻须长度等方面与侧纹云南鳅yunnanilus pleurotaenia(Regan,1904)最为相似,但新种独特的斑纹和上下唇的长乳突可明显与之区别,二者在一些度量特征上也有区别。黄体高原鳅Triplophysa flavicorpus sp．nov．与同分布于西江水系的南丹高原鳅T．nandanensis Lan et al．较为相似,并以下列特征组合与高原鳅属所有已知种相区别：背鳍分枝鳍条10根、臀鳍分枝鳍条6～7根、体被细鳞、侧线完全、具6条宽横斑和1条沿侧线的细纵纹、尾鳍深分又、尾鳍基具1半圆形黑斑、尾鳍上下叶各具2条黑色横斑、腹鳍末端后伸超过肛门、腋部具发达的肉质鳍瓣、上唇中央完全中断等。云南鳅属和高原鳅属均是高原特有类群,前者仅分布于云南东中部地区,后者则集中分布于青藏高原。两个新种的分布地均远离这两个属的分布中心,而且呈间断分布。通过各自相近种谱系关系分析,推测这种特殊的分布格局是通过隔域分化形成的。     

<Emphasis Type="Italic">Erromyzon damingshanensis</Emphasis>, a new sucker loach (Teleostei: Cypriniformes: Gastromyzontidae) from the Pearl River drainage of Guangxi,China

Erromyzon damingshanensis, a new sucker loach is described from the Pearl River drainage in Guangxi, China. The new species Erromyzon damingshanensis is distinguished from the other species of the genus in having a crescentic median lobe of the rostral fold, rostral barbels shorter than rostral fold; postlabial groove broadly interrupted medially, seven branched dorsal fin rays, 16 branched pectoral fin rays, lateral line scales 88–95, caudal peduncle depth larger than its length; body with 12 irregular bars on flank, interrupted on dorsum.     

Reproductive biology of female bigeye tuna Thunnus obesus in the western Pacific Ocean

The reproductive biology of female bigeye tuna Thunnus obesus was assessed by examining 888 fish (ranging from 84·9 to 174·4 cm fork length, L_F) caught by Taiwanese offshore longliners in the western Pacific Ocean from November 1997 to November 1998 and November to December 1999 and 258 gonad samples from these fish. The overall sex ratio of the catch during the sampling differed significantly from 0·5, but males were predominant in sizes >140 cm L_F. Reproductive activity (assessed by histology), a gonado‐somatic index, and the size‐frequency distributions of whole oocytes indicated that spawning occurred throughout the year and the major spawning season appeared to be from February to September. The estimated sizes at 50% maturity (L_F50) of females was 102·85 cm (95% c.i .: 90·79–110·21 cm) and the smallest mature female was 99·7 cm L_F. They are multiple spawners and oocytes develop asynchronously. The proportion of mature (0·63) and reproductively active (0·70) females with ovaries containing postovulatory follicles indicated that they spawn almost daily. Batch fecundity for 15 females with the most advanced oocytes (>730 µm) ranged from 0·84 to 8·56 million eggs (mean ± s.d . = 3·06 ± 2·09). The relationships between batch fecundity (F_B, in millions of eggs) and L_F (cm) and round mass (M_R, kg) were (r² = 0·84) and (r² = 0·80), respectively. The parameters estimated in this study are key information for stock assessments of T. obesus in the western Pacific Ocean and will contribute to the conservation and sustainable yield of this species.     

Satiation meal and the effects of meal and body sizes on gastric evacuation rate in brook trout Salvelinus fontinalis fed commercial pellets

Gastric evacuation (GE) experiments were performed on brook trout Salvelinus fontinalis fed commercial food pellets. The experiments included small fish (36 g; 15 cm total length, L_T) fed meals of 0·2, 0·4 and 0·8 g and large fish (152 g; 23 cm) fed meals of 0·8, 2·0 and 4·0 g at temperatures ranging from 15·1 to 18·2° C. The stomach contents were thereafter sampled and weighed at 3 h intervals until the first empty stomach was observed. The course of GE was examined by use of a general power function of the data that revealed that the square‐root function described the GE rate (GER) by the current stomach content mass independently of original meal size. Using the square‐root function, the relationship between GER and fish size was described by a power function of fish length, whereas the effect of temperature was described by a simple exponential function. GER of the commercial pellets fed to S. fontinalis could thus be described by (g h^?1), where S_t is stomach mass (g) at time t (h), L is total fish length (cm) and T is temperature (° C). The result of this study should provide a useful tool for planning of feeding regimes in production of S. fontinalis by optimizing growth and minimizing food waste.     

Valid oxygen uptake measurements: using high r2 values with good intentions can bias upward the determination of standard metabolic rate

This analysis shows good intentions in the selection of valid and precise oxygen uptake (O₂) measurements by retaining only slopes of declining dissolved oxygen level in a respirometer that have very high values of the coefficient of determination, r², are not always successful at excluding nonlinear slopes. Much worse, by potentially removing linear slopes that have low r² only because of a low signal-to-noise ratio, this procedure can overestimate the calculation of standard metabolic rate (SMR) of the fish. To remedy this possibility, a few simple diagnostic tools are demonstrated to assess the appropriateness of a given minimum acceptable r², such as calculating the proportion of rejected O₂ determinations, producing a histogram of the r² values and a plot of r² as a function of O₂. The authors offer solutions for cases when many linear slopes have low r². The least satisfactory but easiest to implement is lowering the minimum acceptable r². More satisfactory solutions involve processing (smoothing) the raw signal of dissolved oxygen as a function of time to improve the signal-to-noise ratio and the r²s.     

Amblyceps crassioris,a new sisoroid catfish from Odisha,India (Siluriformes: Amblycipitidae)

Amblyceps crassioris, a new species of amblycipitid catfish, is described from the Mahanadi River basin in Odisha, India. The new species can be distinguished from its congeners in having a combination of the following characters: a deeply forked caudal fin, centrally projecting hooks on proximal lepidotrichia of median caudal-fin rays absent, jaws equal in length, lateral line absent, body depth at anus 15.1%–19.5% standard length (SL), caudal peduncle depth 13.0%–18.3% SL, adipose-fin base length 21.1%–27.1% SL, eye diameter 7.35%–14.1% head length and 38 total vertebrae.     

A study on some biological characteristics of Mugil cephalus (L.) in Bardawil Lake, Egypt

Studies on the morphometric characteristics and the age and growth of Mugil cephalus (L.) of Bardawil Lake, Egypt, showed that the regression of body measurements on total length was linear and revealed that the standard length, pectoral fin depth and dorsal fin depth were different than the caudal peduncle and head length. Age and growth studies also showed that a straight line relation was determined between scale radius and body length as expressed by the following equation: Y  =−1.2127 + 1.0850 X . Accordingly, M. cephalus attained mean lengths of 14.2, 20.6, 23.9, 26.4, 28.5 and 30.0 cm at 1 to 6 years of age, respectively. Growth of the species is represented by the von Bertalanffy growth equation as: L _t=45[1−exp−( t − t _o)].     

Morphometric differences among populations of Tu’ini,Capoeta damascina (Teleostei: Cyprinidae), in the interior basins of Iran

Tu’ini, Capoeta damascina, is a widespread species in the interior basins of Iran. To examine the morphometric variations residing within the taxon, six isolated river systems from the west, south, southwest, and centre of Iran were investigated: Ghárásu, Hánnã, Bãzoft, Eghlid, Ãbãdeh, and Gãmãsiyãb. A total of 240 adult fish specimens ≥180 mm standard length (females: 180–336; males: 186–304) were collected from March to June 2008. Based on the multivariate methods used (factor analysis, canonical variates analysis, and a classificatory discriminant analysis), the river samples were clearly separated into distinct groups. The Ghárásu River sample was separated into a distinct group by differences in inter‐nasal distance (iND), inter‐orbital distance (iOD), and barbel length; the Hánnã by iND, iOD, body depth (BD), minimum BD, caudal peduncle (CP) depth, CP width, and pectoral‐anal distance; the Bãzoft by head depth, iND, CP length, and preanal length; the Eghlid by anal‐caudal distance; the Ãbãdeh by postorbital length; and the Gãmãsiyãb River by preorbital length, dorsal fin height and base, eye diameter, BD, preventral length, and pectoral‐ventral distance.     

Morphological variations in bluegill, Lepomis macrochirus, with particular emphasis on growth-related changes

Morphological variations in bluegill, Lepomis macrochirus, including growth-related changes, sexual dimorphism and morphological differences between populations in different habitats, were examined in samples from three reservoirs in Kagawa, Japan. Body measurements demonstrated frequent growth-related proportional changes, particularly in body depth, body width, caudal peduncle length and head length, which all showed relative increases, whereas first dorsal fin length, caudal fin length and orbital diameter became relatively shorter. Body weight increased relatively with growth, with relative growth coefficients of 3.339–3.454 for regressions between total length and body weight. Such body weight increases were likely due to the relative increases in body depth and width, and caudal peduncle depth. Although counts of fin spines, fin rays and gill rakers did not change with growth, those of scales tended to increase. Males were significantly larger than females in body depth, caudal peduncle length, head length and body weight. Sexual dimorphism was also apparent in body coloration during the breeding season. In addition, a number of morphological differences were observed between individuals from different habitats.     

中国平鳍鳅科鱼类一新纪录种

20 0 2年 6月于云南省河口瑶族自治县采集到鱼类标本 3尾 ,经鉴定为我国华吸鳅属鱼类之新纪录种———红河华吸鳅 (Sinogastromyzonchapaensis)。测量标本 3尾均保存在台湾清华大学。体长 35～ 5 0mm。背鳍iii,8;臀鳍ii,5 ;胸鳍xiv～xv ,14～ 16 ;腹鳍x～xi,11～ 12。侧线鳞 6 0～ 6 4。体长为体高的 7 0～ 7 2倍 ,为体宽的 4 3～ 4 6倍 ,为头长的 4 9～ 5 1倍 ,为尾柄长的 5 4～ 6 0倍 ,为尾柄高的 12 7～ 14 0倍 ,为背鳍前距的 2 2倍 ,为腹鳍前距的 2 4～ 2 7倍。头长为头高的 1 8～ 1 9倍 ,为头宽的 0 9～ 1 1倍 ,为吻长的 2 0～2 1倍 ,为眼径的 4 7～ 5 0倍 ,为眼间距的 2 0～ 2 3倍。尾柄长为尾柄高的 2 2～ 2 6倍。头宽为口宽的 3 7～4 6倍。     

A new proposal for measurement of the adjusted mean crowding through consideration of size variability in habitat units

The mean crowding has previously been measured under the assumption that all quadrats or habitat units have the same size, even though the actual habitat units such as seeds or leaves are generally variable in size. A new index, ‘adjusted mean crowding’, which is adjusted for this variability can be given as where Q is the total number of habitat units in the whole area, x_j the number of individuals in the jth habitat unit, and a_j is defined as the ‘relative size’ of the jth habitat unit, i.e. a_y=y_y/(∑y_j/Q) where y_j is the actually measured size of the jth habitat unit. It is expected that and for the uniform distribution and the random distribution ‘per unit size’, respectively. The comparison between and regressions ( analysis) for the egg distribution pattern of Callosobruchus chinensis or C. maculatus proved that the regression is biased by a positive correlation between the egg number per seed and seed size rather than by a density-dependent change in the ovipositional behavior.     

A new species of labrid fish <Emphasis Type="Italic">Oxycheilinus samurai</Emphasis> from the western Pacific Ocean

A new species of labrid fish Oxycheilinus samurai sp. nov. is described on the basis of five specimens from the Ryukyu Islands, Japan, and Panay Island, the Philippines. The new species is most similar to the Indo-West Pacific species Oxycheilinus orientalis in having a slender compressed body, 12 pectoral-fin rays, a blackish blotch around the anterior portion of the lateral-line anterior series, and a dark blotch basally on the membrane between the first and second dorsal-fin spines. However, O. samurai can be distinguished from O. orientalis by the following combination of characters: gill rakers 4 + 7–8; snout rounded with maximum circumference 49.8–63.5 % of standard length (SL); interorbital width 7.7–9.2 % of SL; caudal-peduncle depth 13.8–15.3 % of SL; posterior margin of caudal fin white; black or dark red area just before white posterior margin of caudal fin; poorly defined blackish blotches on inner surface of opercle in preserved specimens.     

Ecological studies of collembolan populations in a pine forest soil IV. Comparison of distribution patterns

The distribution pattern of ten species of Collembola was studied during the four years period from July 1971 to May 1975 in a pine forest soil. The distribution patterns were analysed for two scales of distribution, i. e., the distribution over the plot of 10×10 m² and the micro-distribution within a block sample consisting of 36 contigious units each 2×2 cm² in area, by applying the -m regression method. The fundamental pattern which appeared was quite similar for the species examined and individuals were aggregated in response to the heterogeneity of habitat conditions. The causes of aggregations were discussed with regard to some environmental factors. The relative abundances of 10 species within the collembolan community was examined in relation to the habitat utilization and the relative abundance was not related to the degree of aggregation but rather to the area occupied by individuals. This suggests that the more numerically abundant species tend to occupy broader micro-habitat. Biological meaning of aggregation was discussed in connection with the population biology and community organization of collembola.