Length–weight relationship of nine fish species from Skadar Lake (Adriatic catchment area of Montenegro)

This study provides data on the length–weight relationships (LWR) of nine fish species sampled between 2010 and 2014 from Skadar Lake, Montenegro. Also provided are the first comprehensive data of LWRs for three freshwater fishes for which no LWR information was available in the FishBase data bank. The b parameter values ranged from 2.936 to 3.271, while values of the a parameter ranged from 0.002 to 0.014.     

A review of length–weight relationships of fishes from freshwaters of Turkey

This paper presents 145 length–weight relationships gathered from the literature pertaining to 30 Turkish freshwater fish species belonging to six families. The value of the slope b ranged from 2.04 for Carassius carassius to 3.46 for Scardinus erythroptalmus. The mean value of b was 2.91 (SD = 0.305), which did not differ significantly from 3.0 (t‐test, P > 0.05). The median value of b was 2.95; 50% of the b values ranged from 2.68 to 3.14. The plot of log a vs b was used to detect outliers.     

Daily age determination and growth rates of freshwater fish throughout a regulated lotic system of the Murray‐Darling Basin Australia

To facilitate future research in freshwater fish recruitment response to environmental flow delivery, size‐at‐age and growth models are presented for eight fish species occurring in south‐eastern Australia; three small‐bodied species and the juvenile 0+ age classes of five large‐bodied species. Otolith increments were used to estimate the daily age of golden perch Macquaria ambigua, bony bream Nematalosa erebi, common carp Cyprinus carpio; Murray cod Maccullochella peelii, freshwater eel‐tailed catfish Tandanus tandanus, Australian smelt Retropinna semoni, un‐specked hardyhead Craterocephalus stercusmuscarum fulvus and Murray–Darling rainbowfish Melanotaenia fluviatilis. Linear growth models provided the best fit for length‐at‐age data of juvenile 0+ age large‐bodied species; whereas von Bertalanffy growth functions provided the best fit to length‐at‐age data of small‐bodied species. The results provide novel baseline data for future research in this area.     

Nine polymorphic microsatellite loci in the Neotropical electric eel Eigenmannia (Teleostei: Gymnotiformes)

Ten microsatellite loci were isolated from a species of the Neotropical electric eel, Eigenmannia, a genus of freshwater fish characterized by small populations and low vagility. Nine microsatellites were polymorphic, the number of alleles ranging from seven to 27, and values of observed heterozygosity ranging from 0.327 to 0.741. These loci were developed for population genetic studies of Eigenmannia sp. 2, however, cross‐amplification carried out with other species of this genus as well as other Gymnotiformes genera indicate that these molecular markers are also potentially useful for population‐level studies in closely related species.     

Length–weight and length–length relationships of fishes from the Ouémé River in Bénin (West Africa)

The relationships between total (TL) and standard (SL) lengths for 50 fish species and between TL and wet weight for 52 fish species caught in the Ouémé River are presented. Relationships between TL and SL are linear. Between TL and weight, the relationships are of the form TW = aTL^b. The b values range from 2.3307 to 3.5185. Student's t‐test revealed that 38.5% of the species have b values significantly different from 3.     

A review of changes in the fish assemblages of Levantine inland and marine ecosystems following the introduction of non-native fishes

The arrival of non‐native fishes in the Levant Basin began in the late 19th century. Whereas the presence of most of the 40 non‐native freshwater fishes stem from intentional introductions, either for aquaculture or pest control, the 62 species of non‐native marine fishes arrived by natural dispersal via the Suez Canal. Of the non‐native freshwater species, five have established successful breeding populations (mosquitofish Gambusia affinis, common carp Cyprinus carpio, crucian carp Carassius carassius, swordtail Xiphophorus hellerii and rainbow trout Oncorhynchus mykiss), and seven are regularly stocked in natural habitats (thinlip mullet Liza ramada, flathead mullet Mugil cephalus, European eel Anguilla anguilla, grass carp Ctenopharyngodon idella, Asian silver carp Hypophthalmichthys molitrix, bighead carp Aristichthys nobilis, black carp Mylopharyngodon piceus). Some non‐native species appear to have out‐competed native species. Gambusia affinis may have caused the extirpation of two native cyprinid fishes from the Qishon River basin (Levant silver carp Hemigrammocapoeta nana and common garra Garra rufa) and the southern Dead Sea (endemic Sodom's garra G. ghoerensis). The opening of the Suez Canal in 1869 allowed entry into the eastern Mediterranean of Indo‐Pacific and Erythrean biota, with the latter now dominating the community structure (50–90% of fish biomass) and function (altered native food web) of the Levantine littoral and infra‐littoral zones. The process has accelerated in recent years concurrent with a warming trend of the seawater. Record numbers of newly discovered non‐native species is leading to the creation of a human‐assisted Erythrean biotic province in the eastern Mediterranean.     

Length–weight relationships of fish from Madeira River,Brazilian Amazon,before the construction of hydropower plants

Length–weight relationships (LWRs) are presented for 112 freshwater fish species representing 23 families and five orders captured in the Madeira River, the largest white‐water river tributary of the Amazon River. The allometry coefficient (b) of the LWR (Wt = aSL^b) ranged from 2.446 to 3.856 with a median value of 3.102. Eight new LWR records are presented for Amazonian species as information for FishBase. LWRs in the present study provide historical data on a and b coefficients prior to the damming of the Madeira River in November 2011, allowing comparison estimates of predicted future population parameters as influenced by human intervention.     

All in the ears: unlocking the early life history biology and spatial ecology of fishes

Obtaining biological and spatial information of the early life history (ELH) phases of fishes has been problematic, such that larval and juvenile phases are often referred to as the ‘black box’ of fish population biology and ecology. However, a potent source of life‐history data has been mined from the earstones (otoliths) of bony fishes. We systematically reviewed 476 empirical papers published between 2005 and 2012 (inclusive) that used otoliths to examine fish ELH phases, which has been an area of increasing attention over this period. We found that otolith‐based research during this period could be split into two broad themes according to whether studies examined: (i) biological objectives related to intrinsic processes such as larval and juvenile age, growth and mortality, and/or (ii) spatial objectives, such as habitat use, dispersal and migration. Surprisingly, just 24 studies (5%) explored a combined biological–spatial objective by simultaneously exploiting biological and spatial information from otoliths, suggesting much more scope for such integrated research objectives to be answered via the use of multiple otolith‐based techniques in a single study. Mapping otolith analytical techniques across these two approaches revealed that otolith structural analysis was mainly used to investigate biological processes, while otolith chemical analyses were most often applied to spatial questions. Heavy skew in research effort was apparent across biomes, with most (62%) publications specific to marine species, despite comparable levels of species richness and the importance of freshwater taxa (just 15% of papers). Indeed, around 1% (380 species) of a possible 31400+ extant species were examined in our surveyed papers, with a strong emphasis on temperate marine species of commercial value. Potential model species for otolith‐based ELH ecology research are arising, with the eel genus Anguilla (24 studies) and the European anchovy Engraulis encrasicolis (14 studies) attracting more research effort than most other taxa. While there is a preponderance of common techniques (e.g. daily otolith increment counts, increment widths), novel techniques such as transgenerational marking and computed X‐ray tomography, are increasingly being applied in published studies. The application of an integrative approach based on a combination of emerging techniques and traditional methods holds promise for major advances in our understanding of ELH fish ecology and to shine light into the ‘black box’ of fish ecology.     

Fine‐scale habitat preferences influence within‐river population connectivity: a case‐study using two sympatric New Zealand Galaxias fish species

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Length–weight relationships and length at first maturity for fish species in the upper Miranda River,southern Pantanal wetland,Brazil

Length–weight relationships (LWR) were estimated for 17 species and total length at first maturity (L50) for three species of freshwater fishes from the Miranda River, southern Pantanal, Brazil. The b values were compared for some species in the Paraguay River basin with the northern (Cuiabá River) part of the basin; differences in length–weight relationships were significantly different for Pseudoplatystoma corruscans, P. reticulatum (syn. P. fasciatum). First references on L50 and LWR are presented for two and eight fish species, respectively, as well as the new maximum total length for two species.     

Length–weight relationships of seven myctophid fishes (Myctophiformes: myctophidae) in the South China Sea

The study included 546 specimens of seven myctophid fish species from the South China Sea (captured during June 2015 by bottom and mid‐water trawls). Length‐weight relationships (LWRs), W = aL^b, were estimated using standard length. The species belong to four genera. The values for the parameter a ranged from 0.006 to 0.022, while the b values ranged from 2.710 to 3.476 (Range of r² values: .938 to .971). According to FishBase, this study presents the first LWRs for these species, including two maximum standard lengths for Diaphus chrysorhynchus and Notoscopelus resplendens.     

Length–weight relationships for five fish species caught in Keban Dam Lake,Turkey

Length–weight relationships (LWR) are presented for five commercial freshwater fish species (Luciobarbus esocinus, Heckel, 1843; Capoeta trutta, Heckel, 1843; Barbus lacerta, Heckel, 1843; Luciobarbus mystaceus, Pallas, 1814 and Capoeta umbla, Heckel, 1843) collected from Keban Dam Lake located in eastern Anatolia, Turkey. Studied samples were obtained between July and December 2008 using commercial gill nets. For each species the sample size, length range, weight range, length‐weight relationships, 95% confidence intervals of a and b, coefficient of correlation and growth type are given. Values of b were between 2.915 (Luciobarbus esocinus) and 3.079 (Copoeta trutta) and r² values from 0.919 (Copoeta trutta) to 0.987 (Barbus lacerta) in the study. New maximum length and length–weight relationships are reported for Barbus lacerta and Luciobarbus mystaceus.     

TN : TP ratio and planktivorous fish do not affect nutrient-chlorophyll relationships in shallow lakes

1. In previous work, phytoplankton regulation in freshwater lakes has been associated with many factors. Among these, the ratio of total nitrogen to total phosphorus (TN : TP) has been widely proposed as an index to identify whether phytoplankton are N‐ or P‐limited. From another point of view, it has been suggested that planktivorous fish can be used to control phytoplankton. 2. Large‐scale investigations of phytoplankton biomass [measured as chlorophyll a, (chl‐a)] were carried out in 45 mid‐lower Yangtze shallow lakes to test hypotheses concerning nutrient limitation (assessed with TN : TP ratios) and phytoplankton control by planktivorous fish. 3. Regression analyses indicated that TP was the primary regulating factor and TN the second regulating factor for both annual and summer phytoplankton chl‐a. In separate nutrient–chl‐a regression analyses for lakes of different TN : TP ratios, TP was also superior to TN in predicting chl‐a at all particular TN : TP ranges and over the entire TN : TP spectrum. Further analyses found that chl‐a : TP was not influenced by TN : TP, while chl‐a : TN was positively and highly correlated to TP : TN. 4. Based on these results, and others in the literature, we argue that the TN : TP ratio is inappropriate as an index to identify limiting nutrients. It is almost impossible to specify a ‘cut‐off’ TN : TP ratio to identify a limiting nutrient for a multi‐species community because optimal N : P ratios vary greatly among phytoplankton species. 5. Lakes with yields of planktivorous fish (silver and bighead carp, the species native to China) >100 kg ha^?1 had significantly higher chl‐a and lower Secchi depth than those with yields <100 kg ha^?1. TP–chl‐a and TP–Secchi depth relationships are not significantly different between lakes with yields >100 kg ha^?1 or <100 kg ha^?1. These results indicate that the fish failed to decrease chl‐a yield or enhance Z_SD. Therefore, silver carp and bighead carp are not recommended as a biotic agent for phytoplankton control in lake management if the goal is to control the entire phytoplankton and to enhance water quality.     

Length–weight relationships of fish species in the freshwater rift valley lakes of Kenya

This study reports length–weight relationships for 10 species of fish encountered in the only two freshwater lakes wholly in the Rift Valley of Kenya, Naivasha and Baringo. In Lake Naivasha, none of the species analysed was native to the lake. Two were introduced species non‐native to East Africa (Micropterus salmoides, Cyprinus carpio), with three native to East Africa but not to the lake (Tilapia zillii, Oreochromis leucostictus, Barbus paludinosus). In Lake Baringo, all species were native (Oreochromis niloctictus baringoensis, Labeo cylindricus, Barbus intermedius autralis, Barbus lineomaculatus, Clarias gariepinus). Specimens were collected by gill netting in September 2004 and October 2005. With the exception of B. lineomaculatus, the b values in the relationship W = aL^b were between 2.90 and 3.22.     

Length-weight relationship of seven bycatch fish species caught along the Chennai coast,Bay of Bengal,Eastern Indian Ocean

Length-weight relationships (LWRs) were estimated for seven fish species captured as bycatch along the Chennai coast, Bay of Bengal, Eastern Indian Ocean. Fish samples were collected fortnightly between June-2018 to February-2019 from the commercial boats operating bottom trawl nets with a cod-end mesh size of 35mm. The total length (L) and the wet weight (W) to the nearest 0.1 cm and 0.01 g, respectively which is followed by regression analysis. The values of exponent (b) for LWRs varied from 2.5803 (Parachaeturichthys polynema) to 3.4432 (Ostorhinchus oxina). Similarly, a value varied between 0.0037 (Bleekeria kallolepis) and 0.0258 (Archamia bleekeri). As per FishBase, a new TLmax has been recorded for four species such as Ostorhinchus oxina, Jaydia striata, Bleekeria kallolepis and Cocotropus roseus.     

Dietary effects on fatty acid composition in muscle tissue of juvenile European eel, <Emphasis Type="Italic">Anguilla anguilla</Emphasis> (L.)

The role of intracontinental migration patterns of European eel (Anguilla anguilla) receives more and more recognition in both ecological studies of the European eel and possible management measures, but small-scale patterns proved to be challenging to study. We experimentally investigated the suitability of fatty acid trophic markers to elucidate the utilization of feeding habitats. Eight groups of juvenile European eels were fed on eight different diets in a freshwater recirculation system at 20°C for 56 days. Three groups were fed on freshwater diets (Rutilus rutilus, Chironomidae larvae, and Gammarus pulex) and four groups were reared on diets of a marine origin (Clupea harengus, Crangon crangon, Mysis spec., and Euphausia superba) and one on commercial pellets used in eel aquaculture. Fatty acid composition (FAC) of diets differed significantly with habitat. FAC of eel muscle tissue seemed to be rather insensitive to fatty acids supplied with diet, but the general pattern of lower n3:n6 and EPA:ARA ratios in freshwater prey organisms could be traced in the respective eels. Multivariate statistics of the fatty acid composition of the eels resulted in two distinct groups representing freshwater and marine treatments. Results further indicate the capability of selectively restraining certain fatty acids in eel, as e.g. the n3:n6 ratio in all treatments was <4, regardless of dietary n3:n6. In future studies on wild eel, these measures can be used to elucidate the utilization of feeding habitats of individual European eel.     

Length‐weight relationship and condition factor of 11 fish species of the Igarapé Fortaleza basin,a tributary from the Amazon River system in eastern Amazon (Brazil)

The present study investigated the length‐weight relationship (LWR) and allometric condition factor for 11 freshwater fish species of the Igarapé Fortaleza basin (00°02037.5″N; 51°06019.2″W), a tributary from the Amazon River system in the State of Amapá, northern Brazil. The fish were collected in the period from 2012 to 2014 using gillnets with different mesh sizes (10–40 mm between opposite knots). LWR parameters were estimated had angular coefficient (b) varying from 2.055 to 3.158. The allometric condition factor presented interspecific variation. These data complement the efforts to understand the biology of these Amazonian fish species.     

Condition factor,length–weight and length–length relationships of an endangered fish Ompok pabda (Hamilton 1822) (Siluriformes: Siluridae) from the River Gomti,a tributary of the River Ganga,India

The present study describes the condition factor, length‐weight and length‐length relationships for an endangered freshwater fish species Ompok pabda (Hamilton) of the family Siluridae from the River Gomti in Northern India. The values of regression parameter b ranged from 2.81 to 3.32 (r² > 0.90). During the pre‐monsoon, the allometric coefficient b of the LWR was close to isometric value (b = 3.08) allometric (b = 2.87), although it suggested negative allometric growth in monsoon periods while positive growth in post‐monsoon. The condition factor values ranged from 0.672 to 0.744. Results of the present study could be useful to help in conservation and sustainable fisheries management of this endangered species.     

Risk screening of non‐native freshwater fishes at the frontier between Asia and Europe: first application in Turkey of the fish invasiveness screening kit

The aim of the present study was to assess the invasive potential of introduced non‐native and translocated fishes in Turkey (Anatolia and Thrace) by applying the Fish Invasiveness Screening Kit (FISK), a risk identification tool for freshwater fishes. From independent evaluations by two assessors of 35 species, calibration of FISK for Turkey identified a threshold score of 23, which reliably distinguished between potentially invasive (high risk) and potentially non‐invasive (medium to low risk) fishes for Anatolia (Asia) and Thrace (Europe). No species was categorized as ‘low risk’, 18 species were categorized as ‘medium risk’ and 17 as ‘high risk’ (two being ‘moderately high risk’, nine ‘high risk’, and six ‘very high risk’). The highest scoring species was gibel carp Carassius gibelio, whereas the lowest scoring species was Caucasian dwarf goby Knipowitschia caucasica, a translocated species. Assessor certainty in their responses averaged overall between ‘mostly uncertain’ and ‘mostly certain’, with red piranha Pygocentrus nattereri and topmouth gudgeon Pseudorasbora parva achieving the lowest and highest certainty values, respectively, and with overall significant differences in certainty between assessors. The results of the present study indicate that FISK is a useful and viable tool for identifying potentially invasive non‐native fishes in Turkey, a country characterized by natural biogeographical frontiers.     

Length–weight relationships (LWRs) of 12 Indian freshwater fish species from an un‐impacted tropical river of Central India (River Ken)

The length–weight relationships (LWRs) were studied of 441 fish individuals covering six families, eight genera and 12 freshwater species (L. dyochilus, L. calbasu, L. gonius, L. fimbriatus, P. sarana, L. boggut, C. mrigala, W. attu, B. bagarius, E. vacha, N. notopterus and S. aor) captured in the River Ken (tributary of the Yamuna River) from December 2007 to January 2009. The b value ranged from 3.52 for Cirrihinus mrigala, to 2.11 for Labeo gonius, with a mean of 3.03 at p < 0.001 for all species. The present observations are significant for conservation and management because the Ken River has been approved under India’s first interlinking plan with the River Betwa. The objective was to evaluate the LWRs of the freshwater fish species of an unimpacted and understudied river, which serves as a baseline for comparison to other relatively altered tropical Indian rivers.