Adipose-fin Length Research Articles

Taxonomic and Otolith Shape Parameters of Nine Sympatric Catfishes Commercially Harvested in Pakistan

Abstract Accurate reorganization of harvested species is essential for appropriate fisheries monitoring but often unnoticed. In this study, an attempt was made to provide an accurate species description based on fish taxonomy and otolith shape parameters of nine sea catfishes living in Pakistan. The lapillus, the largest otolith of catfishes, includes the position of the umbo, the structure of the anterior mesial projection (amp), the incisura linea basalis (ilb) and sulcus lapilli marks (slm) in nine ariid catfishes were evaluated. Discriminant function analysis was performed using twenty-two morphometric parameters showed significant variations between the length of the maxillary barbel, adipose length and preorbital length, which were highlighted as basic discriminating characters. Species without barbells, such as Batrachocephalus mino and Osteogeneiosus militaris, were found to be distant. The taxonomic characters of the genera Netuma and Plicofollis overlapped due to a short adipose fin length. Nevertheless, species Arius arius, Sciades sona and Nemapterxy caelatus differed in a moderate adipose fin length. The preorbital length of Netuma bilineata has a short and rounded snout, while N. thalassina has a long and pointed snout, which is a distinguishing characteristic of both species. The coincident use of fish taxonomy and otolith shape parameters is an effective tool for catfish identification could be helpful in appropriate fisheries sampling programs and management in Pakistan whenever implemented.

Description of two new species of Lithoxus (Hypostominae: Loricariidae) from rio Jari and rio Amapá basins, Brazilian Guiana Shield.

Two new species of Lithoxus, a genus diagnosed by possessing a dorsoventrally depressed body, a large round oral disk, and small tooth cusps with few teeth, are described from two drainages of the Guiana Shield: Lithoxus jariensis from the rio Jari basin and L. raso from the rio Raso, rio Amapá basin. The new species, L. jariensis, is distinguished from congeners by having an adipose fin, by the number of branched anal-fin and caudal-fin rays, by color pattern of the body, number of teeth, adipose-fin length, dorsal adipose-caudal distance, caudal peduncle depth, cleithral width, and dorsal-anal distance. Lithoxus raso can be diagnosed from congeners by coloration pattern, by having an adipose fin, by the number of branched anal-fin rays, number of teeth, adipose-fin length, dorsal adipose-caudal distance, caudal peduncle depth, and cleithral width. Greater genetic divergence in mitochondrial cytochrome oxidase subunit I (COI) confirms L. jariensis and L. raso as two new species.

Chrysobrycon yoliae, a new species of stevardiin (Characiformes: Characidae) from the Ucayali basin, Peru

Chrysobrycon yoliae, new species, is described from a drainage flowing into the río Yucamia basin, río Ucayali basin, Peru. Chrysobrycon yoliaeis readily distinguished from its congeners by the anterior tip of pelvic bone situated anterior to the fifth rib (vs. situated posterior to the fifth rib), the presence of 20-26 dentary teeth (vs. 11-19), and the possession of a terminal lateral-line tube between caudal-fin rays 10 and 11 (vs. the absence of this tube, except in C. eliasi). The new species differs from C. eliasiand C. myersiby the presence of teeth on third pharyngobranchial (vs. the absence of teeth on this bone) and also differs from C. eliasiby the dorsal-fin origin situated at vertical through anal-fin rays 5 to 7 (vs. located at vertical through anal-fin rays 8 to 10), the posterior extent of the ventral process of quadrate reaching the vertical through posterior margin of symplectic (vs. not reaching the vertical through posterior margin of symplectic), the dorsal-fin to adipose-fin length 26.8-28.8% SL (vs. 23.9-26.8% SL), and the body depth at dorsal-fin origin 34.4-42.2% SL (vs. 24.1-34.5% SL). A key for the identification of Chrysobryconspecies is provided.

The sexually dimorphic adipose fin is an androgen target tissue in the brown trout (Salmo trutta fario)

An investigation has been described on the relationship of body length, age and sex with adipose fin length and the number of androgen receptor (AR)-containing cells in the adipose fin as a secondary sexual characteristic for brown trout (Salmo trutta fario). Firstly, body and adipose fin lengths of 2- to 5-year-old brown trout were measured. Thereafter, these fish were killed by decapitation, then their sexes were determined, and adipose fins were excised. The cellular bases of AR binding activities in the adipose fins were analyzed with an antibody against human/rat AR peptide. Immunocytochemistry and western blotting techniques were performed with this antibody. Analysis of morphological measurements indicated that body length and age had a linear relationship with adipose fin length. The coefficients of determination for the body length and age were 0.92 and 0.85 in the male fish and 0.76 and 0.73 in the female fish against the adipose fin length, respectively. At 2 years of age, cells in the adipose fin did not exhibit AR immunoreactivity. However, AR-immunopositive cells were abundant in the adipose fin of 3- to 5-year-old fish. Moreover, the number of AR-immunopositive cells was significantly (P < 0.05) high in males and increased with age. These observations indicate that the adipose fin in the brown trout is a probable target for androgen action and that tissue function or development may to some extent be androgen dependent. In addition, it is likely that such an effect will be mediated by specific androgen receptors.

Effects of eutrophication on vendace, Coregonus albula (L.). III. Seasonal morphological variability of vendace from selected lakes in Wielkopolska

The aim of the study was to determine and compare the most important morphometric and meristic characters of vendace from four lakes located in the Wielkopolska region: lakes Dominickie, Gorzynskie, Lubikowskie, and Strzeszynskie. Biometric analyses were conducted based on the method developed by Prawdin. All morphometric characters are presented in relative values (%) of fork length (longitudo caudalis) according to the method developed by Smitt. Moreover, values of 14 meristic characters were also determined. The greatest differences in values of morphometric characters of vendace were recorded for measurements of head shape, including lateral head length, eye diameter, and postorbital distance, and adipose fin length. The smallest differences in the values of morphometric characters were observed in the largest linear body measurements, i.e., body length, predorsal distance, minimum body depth, and dorsal and anal fin lengths. Variation in morphometric characters in vendace from different lakes confirms the hypothesis that a specific form of vendace is found in each lake. Differences were found in the values of linear measurements of vendace caught in different seasons, which indicates that drawing conclusions on body conformation in vendace is justified only when they are caught in comparable periods of the year.

MORPHOLOGICAL FEATURES USED TO IDENTIFY CHINOOK SALMON SEX DURING FISH PASSAGE

We compared several external morphological features for determining sex of adult fall-run chinook salmon (Oncorhynchus tschawytscha) migrating to spawning grounds in the Central Valley of California. Adult fish carcasses of known sex were measured at fish hatcheries or during angler surveys. These data were used to develop predictive morphometric discriminant function models for potential incorporation in an automated monitoring system. The best predictor for determining sex of handled fish was snout length to fork length ratio, which correctly classified 96% of individuals tested. In contrast, adipose fin length to fork length ratio was the best predictor of sex when measurements were obtained from video images at a fish passage facility. Of these fish, 86% were correctly identified. Combining both ratios with a third (head length) increased model accuracy to 92% for video images.

Early morphological predictors of maturity in one-sea-winter Atlantic salmon

Early separation of maturing from immature fish would be very valuable in Atlantic salmon (Salmo salar) culture. Possible morphometric predictors of maturation in one sea-winter Atlantic salmon were investigated from measurements of body weight, length and depth and adipose fin length undertaken at 14 day intervals from May until August in a population of 80 individually tagged fish, 61 (male and female) of which were subsequently found to be maturing (i.e. grilse). Stepwise discriminant analysis revealed that a combination of forklength and condition factor proved to be the strongest and most consistent predictor of maturation (over 88% accurate) until August. In August when maturing fish could be easily distinguished by shape and colour, forklength and condition factor no longer had any discriminatory power, but body depth at the anal and dorsal fins were good predictors. A second trial was performed on a separate stock of fish for which the same predictors proved robust. The discriminant functions derived from one stock of fish did not, however, produce the same discriminatory power when applied to the other stock. Hence there does not appear to be a simple mathematical means for the general discrimination of maturing and immature salmon. However the morphological predictors described above could be used for visual discrimination when ‘grilse grading’.

A simple non-destructive biometric method for estimating fat levels in Atlantic salmon, Salmo salar L., parr

. Simple body measurements were used to predict the fat content of Atlantic salmon parr. For three different sizes (wet weights 18–98g, 44–207g and 137-151·8g) at two times of year (November/December and July) the percentage body fat (as measured by lipid extraction) could be predicted accurately using multiple regressions based on a combination of the following measurements: wet weight, fork length, opercular height, dorsal height, opercular width, dorsal width, anal width, adipose fin length and condition factor. In every case predictions based on multiple regression equations were more accurate than condition factor alone. This biometric method is easily employed and can potentially be used both in biological studies and on fish farms to assess body condition of individual fish. Since it is non-destructive it has the additional advantage of allowing repeated monitoring of fat levels in the same fish.

Sexual dimorphism in length of upper jaw and adipose fin of immature and maturing Pacific salmon ( Oncorhynchus)

Sexual dimorphism of upper jaw length and adipose fin length was investigated for different size classes of Pacific salmon in order to evaluate if these characters can be used to determine externally the sex of maturing and mature salmon. There was no significant sexual dimorphism in the two morphometric characters for salmon 130 mm fork length. Dimorphism was present in chinook salmon ( Oncorhynchus tshawytscha) 280 mm fork length, but it was not of sufficient magnitude to allow for reliable external identification of the sexes. At 430 mm fork length, the dimorphism in jaw length in coho salmon ( O. kisutch) was marked enough to identify correctly 88% of the males and 98% of the females. The dimorphisms were more marked at larger body lengths and in individuals closer to sexual maturity. Females were always identified more accurately as to their sex than were males at all body lengths. The sex of salmon can be determined externally by examination of upper jaw length if the individual is of appropriate size.

The commercial exploitation of sea trout, Salmo trutta L.

. The net and coble catch of sea trout in the River North Esk was sampled between 1977 and 1979. A comparison of the length frequency distribution of these samples with those of sea trout taken in a trap which was assumed to be unselective revealed that the net and coble fishery was very selective. Only isolated fish below 35·0 cm were encountered in the commercial catch samples, yet between 25% and 41% of the upstream migratory sea trout taken in the trap during the netting season were below this length. The sea trout in the commercial catch samples were predominantly maiden, one-sea-winter fish. The dominant age class each year was the 2·1 + group, 3·1 + fish comprising the other major age class. The freshwater age of the maiden sea trout sampled declined as the season progressed. The proportion of previously spawned fish in the samples ranged between years from 12% to 15%. The mean length and mean weight of sea trout sampled from each year's catch showed little variation, ranging from 42·9 cm to 43·3 cm and 971 g to 972 g, respectively. The ratio of males to females in the 1979 sample was 1·00:2·18. The use of morphometric characteristics, including head length, pectoral fin length and adipose fin length was investigated with the aim of distinguishing the sex of fish taken early in the season from external features alone. Although in each month the mean head length as a percentage of fork length of males was greater than that of females, this difference was not sufficient to enable the rapid determination of sex during commercial catch sampling routines. The exploitation rate of sea trout reaching the most upstream major fishing station, Morphie Dyke, was estimated from the recapture of upstream adult sea trout removed from a trap and released in the main river 2 km downstream of Morphie Dyke. The percentage exploitation rate at this fishing station was found to range between 6·4% and 12·2%, and the percentage exploitation rate for the entire net and coble fishery was at a level of approximately 30% during the period of the study. The sea trout statistics of the North Esk net and coble fishery for the period 1925–1979 were examined, and the effect of a change in fishing effort on these figures is described. Recent catch figures, although below those reported during the mid-1960s, are above the level of catches reported prior to 1952.