Length–weight relationships of poor cod (Trisopterus minutus Linnaeus, 1758) in the Central Aegean Sea

A total of 1527 specimens of poor cod, Trisopterus minutus, was collected by trawl fishing between April 2001 and March 2002 from the ?zmir Bay (Middle Aegean Sea). Fish size ranged from 10.6 cm total length (TL, minimum) in September to 24.8 cm TL in April. Of the sampled population 53% were males and 41% females (sex ratio female : male = 1 : 1.3). Length–weight relationships were determined for males, females and combined sexes as W = 0.007L^3.16, W = 0.009L^3.04 and W = 0.007L^3.14 respectively.     

Life history of the Western Crested Loach <Emphasis Type="Italic">Paracobitis malapterura</Emphasis> in the Zarrin-Gol River,East of the Elburz mountains (Northern Iran)

A total of 370 specimens of Paracobitis malapterura in the Zarrin-Gol River (east of the Elburz Mts, Iran) were caught by regular monthly collection throughout one year from November 2006 to October 2007. The specimens were then examined for age and growth, reproduction and feeding attributes. Based on otolith readings the maximum ages of the population observed were 3⁺ years for males and 4⁺ years for females. The specimens ranged in size from 38 to 130 mm total length, weighing from 0.68 to 30.55 g total weight. Length-weight relationship was estimated as W = 0.020L ^2.62 for males, W = 0.002L ^3.81 for females and W = 0.008L ^3.08 for the population. Sex ratio was 1: 1.27 in favor of females. The Gonadosomatic index indicated that reproduction of the loach in the river occurred around April–May, with the highest average value of 1.48 for males and of 5.36 for females in May. The absolute fecundity ranged between 92–1180 eggs with a mean of 456.31 eggs. Diameter of oocytes ranged from 0.11 to 2.80 mm with a mean value of 0.95 mm. The absolute fecundity and oocyte diameter to fish size (length and weight) and age were not significantly correlated. Plecoptera and Trichoptera dominated the diet contents composing 72.43% and 20.80% of total frequency of food items, respectively.     

Reproductive biology of the Japanese butterfish,Psenopsis anomala,in the waters off southwestern Taiwan

The dramatic decline in annual yield of the Japanese butterfish, Psenopsis anomala, in southwestern Taiwan over the past decade suggests that this stock might have been overexploited. However, its fishery biology and stock status is poorly understood. This study therefore provides the first information on P. anomala reproductive biology based on 983 specimens collected by small trawlers in southwestern Taiwan waters between February 1999 and February 2000. The sex ratio, 0.44 (431/983), differed significantly from 0.5 and females predominated in fork length above 180 mm. The relationships between body weight (BW) and fork length (FL) were estimated as BW = 1.62 × 10^?4 × FL^2.637 (r² = 0.74; n = 430, P < 0.01) for females and BW = 1.28 × 10^?4 × FL^2.671 (r² = 0.82; n = 552, P < 0.01) for males. Oocytes were mature at 0.5 mm in diameter or larger, and transparent eggs were found at diameters of 0.85 mm. Mean fecundity was estimated at 171 900 ± 61 700 and fecundity (F) was found to increase exponentially with gonad weight (GW) F = 5.4967GW^0.511 (n = 132, r² = 0.74). Mean batch fecundity was estimated to be 83 400 ± 44 600, and relative fecundity from 377 to 2588 (mean 1040) per gram body weight. Logistic curves describing the relationship between proportion of maturity (Pr) at each length interval and fork length were estimated as Pr = 1/(1 + e^{11.4194?0.0749FL}) (r² = 0.99, n = 351) for females and Pr = 1/(1 + e^{11.5113?0.0732FL}) (r² = 0.99, n = 258) for males. Size at 50% maturity was estimated as 15.7 and 15.3 cm FL for females and males, respectively. A multi‐spawning pattern was observed in the Japanese butterfish whereby it spawns throughout the year with a peak from February to July. A seasonal closure from April to July (spawning season for most fish species) can provide better breeding opportunities for adults and is believed to be a good fishery management measure for this species.     

The reproductive traits of Scomber japonicus (Houttuyn, 1782) in the Eastern Adriatic Sea

The aim of the present study was to investigate the fisheries biology of Scomber japonicus (Houttuyn, 1782) in the Adriatic Sea, to enable implementation of appropriate regulatory measures for fisheries. Reproductive biology and sexual patterns of S. japonicus (chub mackerel) were examined from monthly random samples of commercial catches from purse seine nets (10 mm stretched mesh size) in the eastern Adriatic Sea. The annual mean chub mackerel fork length (FL) was examined from 1998 to 2007. Average fork lengths were approximately 25 cm between 1998 and 2002, decreasing to 22 cm between 2003 and 2007. In addition, sex ratios fluctuated as a function of size and month: females were more abundant in the smaller length classes, as well as before and after spawning; males were more abundant in the larger length classes and during spawning. The overall sex ratio was 0.68; females were significantly predominant. 50% of the chub mackerel population was sexually mature at a FL of 18.3 cm, and both males and females reached sexual maturity at FLs of 20.4 cm and 16.8 cm, respectively. Based on gonad maturity stages, gonad weight and gonadosomatic index, chub mackerel spawned from May to August, with peak spawning in June for both sexes. The mean absolute fecundity was 181 277 ± 62 090 oocytes per ovary. A positive exponential correlation was found between fecundity and fork length, gonad weight, and total chub mackerel weight (r² = 0.640; r² = 0.686 and r² = 0.607, respectively).     

Some biological characteristics of Hemigrammocapoeta kemali (Hanko, 1924) in Işıklı Lake (Denizli-Turkey)

Totals of 284 Hemigrammocapoeta kemali specimens were caught during 1998 in the I??kl? Lake, Turkey. Their ages, lengths and weights were determined to estimate length–weight relationships and age composition. Fecundity and oocyte diameter were also determined. The sex ratio was 1 : 1.29. Fork length and total weight of specimens ranged from 3.4 to 8.2 cm and from 0.5 to 6.9 g, respectively. Maximum age observed was 4 years. The length–weight relationship for all fish was best described by the equation W = 0.0121*L^3.06; the von Bertalanffy growth equations for length and weight were Lt = 8.73[1?e^{?0.401(t + 0.947)}]; Wt = 9.17[1?e^{?0.401(t + 0.947)}]^3.06. Oocyte numbers varied from 220 to 1159 and oocyte diameters ranged between 450 and 900 μm.     

Morphometric analysis of otoliths of juvenile crucifix sea catfish Sciades proops (Valenciennes, 1840)

The objective of this study was to analyze the morphometry of otoliths for Sciades proops juveniles by testing the hypothesis of equality in morphometric relationships for the right and left otoliths, which could then be interchangeably used to estimate fish size or weight. Samples were obtained monthly directly from anglers after each event that took place off the state of Sergipe from March/2014 to April/2015. Anglers used rod and reel during these events, with no restriction on hook size or line thickness. Each fish specimen sampled had their total weight (W, g) and total length (TL, cm) measured and their lapillus otoliths removed and stored separately. Each otolith had its length (OL), width (OWi), and thickness (OT) measured (all in mm) under a stereomicroscope. Otoliths were weighed using a precision scale (OW, g). A total of 883 specimens were sampled: TL = 12.0–60.5 cm and W = 9.8–1880 g. The weight‐length relationship for the juvenile fishes was W = 0.0052TL^3.086 and for their otoliths was OW = 0.0002OL^3.177. The weight‐length and length‐length relationships fitted for each otolith (right and left) were not statistically different and thus all relations were estimated for grouped otoliths. The length‐length relationships for the otoliths were: OWi = 0.947OL?0.205 and OT = O.484OL?0.698. The relationship estimated for juvenile fish and otolith weight was Wj = 1076.1OW?9.120. For juvenile fish total length and otolith length, width and thickness, the following relationships were estimated: TLj = 4.028OL?3.199, TLj = 4.208OWi?2.091, and TLj = 7.824OT + 3.659, respectively. Relationships between fish and otolith size, and between fish and otolith weight indicated a change in slope close to L_m50, which should be better explored when more adult specimens are available.     

Length–weight relationships of two sympatric species (Knipowitschia byblisia Ahnelt, 2011 and K. caunosi Ahnelt, 2011) in Köycegiz Lake,Turkey

This study provides basic information on length–weight relationships for Knipowitschia byblisia Ahnelt, 2011 and Knipowitschia caunosi Ahnelt, 2011, two endemic species of Köycegiz Lake Basin (Southern‐West of Turkey). Samplings were carried out seasonally from 2014 to 2015 by means of beach seine nets with mesh sizes from 10 to 35 mm. A total of 343 individuals from the two fish species were examined, with more specimens belonging to K. byblisa (90.4%). The total length–weight relationships were calculated as: W = 0.0054 TL^3.384for K. byblisia and W = 0.0058 TL^3.417for K. caunosi, respectively.     

Maturity and fecundity of golden grey mullet (Liza aurata Risso, 1810) in Iranian waters of the Caspian Sea

The objective of the study was to determine some reproductive parameters in the golden grey mullet (Liza aurata Risso, 1810) during two periods half a decade apart while also trying from limited data to identify changes in fecundity over the past half century. Maturity and fecundity of golden grey mullet caught in Iranian waters of the Caspian Sea is not well documented and were thus studied during several seasonal cycles during 2002–2004 to establish basic data on reproduction in the area. The fork length (FL) of 462 sampled fish was between 22.1 and 51.9 cm. The fork length–weight relationship derived from all fish was W = 0.0118FL^2.964. Overall male to female ratio was 1 : 1.42. The reproductive season extended from October to December. Fifty percent of sexual maturity was at FL 26.0 cm. Mature gonads were present in 20% of fish at age 3, 63% at age 4, 88% at age 5, and 97% at age 6. Individual absolute fecundity of the golden grey mullet ranged from 113 386 to 1.47 million eggs, with a mean (±SD) of 451 963 (±274,114.2). An overlap exists between the spawning and fishing seasons. Therefore, the start of the fishing season should be delayed for 1 month in order for stocks to complete their spawning.     

Size composition and reproductive biology of the ornate jobfish <Emphasis Type="Italic">Pristipomoides argyrogrammicus</Emphasis> (Lutjanidae) off Ishigaki Island,Okinawa

The ornate jobfish Pristipomoides argyrogrammicus is an important lutjanid species for fisheries in the Okinawan region of Japan. The present study estimated the size composition and reproduction of this species in the waters around Ishigaki Island, Okinawa Prefecture. The length–frequency distribution indicated that males grow larger than females. The fork length (FL; mm)–whole body weight (BW; g) relationship and FL–total length (TL) relationship were as follows: BW = 1.048 × 10⁻⁵ FL^3.121 and TL = 1.101 × FL + 2.196, respectively. The main spawning season was estimated as between April and August, since higher gonadosomatic index (GSI) values were found for both sexes, and matured oocytes were observed in females during these months. The developmental stage of ovaries correlated with the GSI of females. Fecundity ranged from 9,530 to 98,260 oocytes in fish of 177.0 to 278.0 mm FL, and the FL–fecundity relationship was as follows: fecundity = 9.525 × 10⁻⁸ FL^4.903.     

Length–weight relationships of two endemic species of Alburnoides nicolausi (Bogutskaya & Coad, 2009) and Alburnus zagrosensis (Coad, 2009) in Houzian River,Lorestan Province,Iran

This investigation prepares the length–weight relationships (LWRs) of two fish species, including Alburnoides nicolausi (Bogutskaya & Coad, 2009) and Alburnus zagrosensis (Coad, 2009) from Houzian River (latitude 33°22′15.20″ to 33°21′31.57″N; longitude 49°44′39.66″ to 49°44′17.67″E), Lorestan province, Iran. Fish specimens were collected monthly using seine net with 5 mm (Stretched) mesh size between April to September 2017. The LWRs for fish species were W = 0.0059L^3.405 (male) and W = 0.0053L^3.494 (female) for A. nicolausi, W = 0.0035L^3.341 (male) and W = 0.003L^3.387 (female) for A. zagrosensis, respectively. The highest value of r² was .931 for male of A. zagrosensis and lowest value was .964 for male of A. nicolausi.     

Length–weight relationships of wild and farmed Tor putitora from Pakistan

Length–weight relationships (W = a TL^b) were estimated for wild and farmed Tor putitora obtained from River Korang, Islamabad and Attock District, Pakistan, respectively. The results indicate, W = 0.0171 TL^2.85 for wild and W = 0.1000 TL^2.33 for farmed. Total length ranged from 18.0 to 40.2 cm for male and 31.6 to 37.0 cm for female wild Tor putitora, indicating that the fish are now much smaller. The first reference of length–weight relationships for Tor putitora is provided.     

Age and growth of Atlantic bluefin tuna, Thunnus thynnus (Osteichthyes: Thunnidae), in the Mediterranean Sea

The objective of the study was to describe the biometry of Mediterranean bluefin tuna, Thunnus thynnus, the biology of which is not yet well understood. A total of 504 specimens was collected from 1998 to 2005 in the central part of the Mediterranean basin. They were sexed and measured; fork lengths (FL) ranged from 51.0 to 255.0 cm while body weights (W) ranged from 2.6 to 247.0 kg. The first spiniform ray (spine) of the first dorsal fin was removed and cross‐sectioned near the condyle base in order to count annuli for age estimation. The regression coefficient (b) of the female FL–W relationship was significantly higher than that of the male, and both sexes displayed a negatively allometric growth (b < 3); male regression equation: ln W = ?2.942 + 2.730 ln FL; female regression equation: ln W = ?3.660 + 2.878 ln FL. Based on counts of the translucent zones in the sections of the first ray of the first dorsal fin, estimated ages ranged from 1 to 15 years for males and 1 to 14 years for females. The correlation between the spine ray (R) and FL fit the allometric model best; the R–FL regression equations of the two sexes did not differ significantly and the overall equation was: ln FL = 3.721 + 0.851 ln R. Due to the R–FL allometric correlation, estimates of fork lengths at previous ages, FL_i, were back‐calculated with a body proportional hypothesis. Von Bertalanffy growth equations were derived from both observed and back‐calculated FLs‐at‐age, which did not differ significantly. Moreover, no significant difference was found between the growth equations of the two sexes; the overall equation was FL_t = 373.08 [1?e^{?0.07(t + 1.76)}]. Weight‐at‐age values were derived from the von Bertalanffy predicted FLs‐at‐age by the FL–W correlation equations for males and females. The paper represents the first comprehensive study on the biometry, including age and growth, of bluefin tuna captured in the Mediterranean Sea.     

The relationships between fish size and otolith dimensions in the common sole (Solea solea (Linnaeus, 1758)) captured in the Northeastern Mediterranean

Fish specimens were captured by a commercial bottom trawler at a depth of 50–80 m from Iskenderun Bay (Hatay, Turkey) between December 2017 and May 2018. The bottom trawl gear used was equipped with a 44 mm stretched mesh size net at the cod-end. Blind side and eyed side otolith lengths (OL), otolith breadths (OB) and otolith weights (OW) were measured from each specimen to the nearest 0.001 mm and 0.0001g respectively. A total of 110 fish (43 females and 67 males) were collected. Total length ranged from 20.8 to 28.2 cm and 68.0 to 166.1 g (males) and 21.1 to −28.5 cm and 74.5 to 201.4 g (females). The coefficients of determination between fish weight and otolith weight, and total length and otolith weight (sexes combined) were found as R² = .7694 (0.77) and R² = .6274 (0.63), respectively. A moderate positive relationship between the total length-otolith dimensions, and fish weight-otolith dimensions, was also demonstrated.     

Age and growth of early-life-stage Atlantic tarpon (Megalops atlanticus) from the northcentral Gulf of Mexico

Age and growth of early-life-stage Atlantic tarpon Megalops atlanticus collected from Mississippi coastal waters in the northcentral Gulf of Mexico (GOM) are described using otolith microstructure analysis. Tarpon leptocephali (n = 95, 16.0—27.8 mm standard length, L_S) collected from June throughOctober 2013—2018, ranged in age from 22 to 43 days (mean = 30.9 ± 0.5 days). Leptocephalus somatic growth rates ranged 0.46—1.24 mm day⁻¹ (mean = 0.76 ± 0.02 mm day⁻¹), and leptocephalus otolith growth rates ranged 1.78—3.97 μm day⁻¹ (mean = 2.58 ± 0.04 μm day⁻¹). Growth rates were inversely correlated to leptocephalus age, indicating the shrinkage phase associated with leptocephalus metamorphosis. Juvenile tarpon (n = 358, 50—359 mm fork length, L_F) were collected from August through December 2007—2018. Juveniles exhibited a positive allometric relationship (adjusted R² = 0.99, P < 0.001) between length and mass. The age of 100 juveniles (71—277 mm L_F) ranged from 76 to 174 days. Juvenile growth rate was estimated as 1.56 ± 0.11 mm day⁻¹. Significant (P < 0.001) linear relationships were found between juvenile age and otolith metrics, including otolith mass (R² = 0.81) and radius (R² = 0.68). Evaluation of the backcalculated hatch dates suggests that specimens in the collection hatched from late May through mid-September with slight peaks during July and August. A Rao's Spacing Test of Uniformity indicates the presence of significant lunar periodicity in leptocephalus hatch dates (n = 95, U = 250.1, P < 0.05), with 50% of the leptocephali hatched within 5 days (before or after) of the full moon. This study fills critical gaps in the scientific knowledge of tarpon and provides estimates of early-life-history metrics for an iconic game fish at the northernmost extent of its GOM range.     

Length–length and length–weight relationships of oilfish (Ruvettus pretiosus), escolar (Lepidocybium flavobrunneum), snake mackerel (Gempylus serpens), and longnose lancetfish (Alepisaurus ferox) from the Gulf of Mexico and the western North Atlantic Ocean

Oilfish, escolar, snake mackerel (order Aulopiformes, family Gempylidae), and longnose lancetfish (order Perciformes, family Alepisauridae) sampled from the western North Atlantic and the Gulf of Mexico were analyzed for length–weight and length–length relationships. These species are encountered as occasional bycatch of pelagic longline fisheries. The fish (161 specimens, 19.0–149.1 cm TL) were collected over a 3‐year period (January 2007–January 2010) from pelagic longline gear targeting swordfish and tuna. For each species, 95% confidence limits (CI) of parameters b and log a and regression coefficients (r²) were calculated for log‐transformed length–weight relationships. The length–weight parameter b for all species ranged from 2.881 to 3.358, with regression coefficients (r²) ranging from 0.75 to 0.98. Linear relationships between fork lengths, standard lengths, and total lengths were also calculated.     

Life history traits of Aphanius ginaonis Holly, 1929 (Cyprinodontidae) and potential risks of extinction in the Geno hot spring (Iran) population

This study presents some traits of the Aphanius ginaonis life history in the Geno hot spring and explains the potential risks of its extinction. Sampling was from March 2009 to February 2010. A total of 61 males and 71 females were measured (total length) and weighed, with data on reproductive biometry also taken. Growth parameters were determined in addition to weight–length relationships: W (t) = 0.012TL^3.42, R² = 0.96 for females and W (t) = 0.0101TL^3.38, R² = 0.94 for males. A. ginaonis females showed an asymptotic total length (TL_∞) of 53.03 mm; the growth coefficient, K (year^?1) 0.15, t₀ (year) 1.01; and natural mortality coefficient M (year^?1) 0.62. In males the value for TL_∞ was 48.83 mm; for K (year^?1) 0.2, t₀ (year) 0.44; and M (year^?1) 0.49. The relationship between absolute fecundity and fish size (total length, body weight or age) showed a strong correlation to body weight. The A. ginaonis population is threatened with extinction – and a co‐management in cooperation with the local population for strong protection measures is urgently needed.     

Length–weight relationships of three caught flatfish using shrimp trawler in Motaf fishing grounds,Bushehr province (Persian Gulf)

This study provides length–weight relationships (LWRs) for three flatfish species: Cynoglossus bilineatus (Lacepède, 1802), Solea elongata (Day, 1877), and Pseudorhombus elevatus (Ogilby, 1912) from Motaf fishing grounds (latitude 27°00′ to 28°03′N; longitude 51°41′ to 52°11′E), Bushehr province, Iran. A total of 103 fish specimens were collected using shrimp trawler with 40 mm (stretched mesh size) at depths of 10–30 m between August and September 2017. The LWRs for fish species were W = 0.0019L^3.353 for C. bilineatus: W = 0.0093L^3.174 for S. elongata, and W = 0.006L^3.181 for P. elevatus, respectively.     

The life history of rock gurnard (Trigloporus lastoviza, Brünn. 1768) in the Saronikos Gulf

Age, growth and reproduction of rock gurnard in the Saronikos Gulf (Greece) were studied. Otoliths from 638 specimens (sex combined) were read for age determination. The body length-otolith radius relationship was found linear (L = -18.0 + 4.99 _xR; where L = fish length in mm, R = otolith radius 20 X). The life span of females seemed to be longer than that of males, indicating a differential mortality with sex. The growth was lower than that in the Catalane Sea. The maximum age of fish collected was VIII and the maximum fork length estimated by von Bertalanffy equation was 356 mm. Weight increased as the 3.054252 power or the length. Reproduction was observed to take place between winter and early spring and occasionally in early winter. Males began to mature after completion of the second year and the females after the third. The exploitation rate was rather high, which suggests that the rock gurnard stock was overfished in Saronikos Gulf. The male to female ratio was usually 1:1.     

Reproduction and feeding of the mountain mullet,Agonostomus monticola,in Trinidad,West Indies

Synopsis Reproduction and feeding were studied in mountain mullet,Agonostomus monticola, in northeast Trinidad during the period January 1987 to September 1988. Macroscopic and microscopic examination of the gonads indicated a single, distinct reproductive season from June to October during the wet season. Evidence implies only one spawning event per individual during the reproductive season. Females significantly outnumbered males resulting in a sex ratio of 20.4:1. The mean size at maturity for females was 135 mm fork length (FL). Fecundity (F) is related to size by the equations F = 167.3 FL^2.7 and F = 16430.7 G + 235079 (G = gutted weight).A. monticola was found to be an omnivorous feeder. The dominant food groups found in the stomachs were insects, prawns, fruits and algae, in order of decreasing importance.     

Proposed standard weight (Ws) equation for European perch (Perca fluviatilis Linnaeus, 1758)

Relative weight (W_r) is an important and commonly used condition index that provides a measure of the well‐being of a fish population by comparing the actual weight of a specimen with the ideal weight of a specimen of the same species and of the same length in good physiological condition, i.e. the standard weight (W_s). Two methods of calculating the standard weight are proposed in the literature: the RLP method and the EmP method. The aim of this study was to develop a standard weight equation for European perch by means of both methods, using length–weight data from 64 913 fish from 18 countries (across Europe and Oceania). The resulting equations were: log₁₀ (W_s) = ?3.1483 + 1.2663 log₁₀ (TL) + 0.4291 [log₁₀ (TL)]² for the EmP method and log₁₀ (W_s) = ?5.3493 + 3.2152 log₁₀ (TL) for the RLP method. The applicable length‐range of the two W_s equations was restricted to 80–460 mm. A further research aim was to compare the performances of RLP and EmP. The resulting quadratic EmP W_s equation did not exhibit length‐related biases, which suggests that it can be used to compute relative weight for European perch.