Effects of low temperature on growth and metabolism of larval green sturgeon (Acipenser medirostris) across early ontogeny.

Southern Distinct Population Segment (sDPS) green sturgeon spawn solely in one stretch of the Sacramento River in California. Management of this spawning habitat is complicated by cold water temperature requirements for the conservation of winter-run Chinook salmon. This study assessed whether low incubation and rearing temperatures resulted in carryover effects across embryo to early juvenile life stages on scaling relationships in growth and metabolism in northern DPS green sturgeon used as a proxy for sDPS green sturgeon. Fish were incubated and reared at 11 °C and 15 °C, with a subset experiencing a reciprocal temperature transfer post-hatch, to assess recovery from cold incubation or to simulate a cold-water dam release which would chill rearing larvae. Growth and metabolic rate of embryos and larvae were measured to 118 days post hatch. Reciprocal temperature transfers revealed a greater effect of low temperature exposure during larval rearing rather than during egg incubation. While 11 °C eggs hatched at a smaller length, log-transformed length-weight relationships showed that these differences in developmental trajectory dissipated as individuals achieved juvenile morphology. However, considerable size-at-age differences persisted between rearing temperatures, with 15 °C fish requiring 60 days post-hatch to achieve 1 g in mass, whereas 11 °C fish required 120 days to achieve 1 g, resulting in fish of the same age at the completion of the experiment with a ca. 37-fold difference in weight. Consequently, our study suggests that cold rearing temperatures have far more consequential downstream effects than cold embryo incubation temperatures. Growth delays from 11 °C rearing temperatures would greatly increase the period of vulnerability to predation in larval green sturgeon. The scaling relationship between log-transformed whole-body metabolism and mass exhibited a steeper slope and thus an increased oxygen requirement with size in 11 °C reared fish, potentially indicating an energetically unsustainable situation. Understanding how cold temperatures affect green sturgeon ontogeny is necessary to refine our larval recruitment estimations for this threatened species.

Characterization of a Peruvian coastal fishery targeting the Pacific guitarfish Pseudobatos planiceps.

From December 2012 to June 2014, 796 Pacific guitarfish were caught in 183 fishing sets in northern Peru. Catch occurred in 86.3% of sets. Most individuals caught were mature with a bias toward males. The mean total length for females and males was 83.4 cm, and 91.1 cm, respectively. The capture per unit effort (CPUE) was 12.6 ± 3.4 guitarfish (km.12 h)-1. The length-weight relationships showed that this species presents a sexual dimorphism in growth. These results support the importance of Sechura Bay as a key area for this species. This study represents the first species-specific fishery data for the Pacific guitarfish.

Determination of Growth Indicators of Tilapia sparrmanii (Smith, 1840) in Molepo Dam, South Africa.

<b>Background and Objective:</b> The sustainable management and conservation of fish biodiversity depends on studying fish biology. In this study, the length-weight relationships and condition factors of <i>Tilapia sparrmanii</i> were observed to gain a better understanding of their ecological and nutritional conditions. This information is crucial for the effective management of fisheries. <b>Materials and Methods:</b> During the study, 100 <i>T. sparrmanii</i> were collected from the Molepo Dam from October, 2022 to March, 2023. This fish's condition factor (CF) and length-weight relationship (LWR) were studied. To determine the size of each fish, the total length was measured using a caliper with a precision of 0.1 mm and the weight using a balance with an accuracy of 0.1 g. Differences were analyzed using ANOVA with the Tukey's <i>post hoc</i> test. A non-parametric Chi-square test was employed to evaluate the differences in sexes each month. <b>Results:</b> Their total length and body weight ranged from 4-15 cm and 0.96-57.96 g, respectively. The study found a strong positive relationship between the length and weight of the fish (r = 0.96). The regression coefficient (b) was more than 3.0, indicating a positive allometric growing rate. The condition factors (K) of males and females were not significantly different (p>0.05). The lowest CF value was observed in March (K = 1.01±0.03) and the highest in December (K = 1.73±0.12). The sex ratio of 1.0 male to 1.15 female was observed, which was significantly different from the theoretical ratio of one male to one female. This suggests that males were not significantly more than females (p>0.05). <b>Conclusion:</b> The study found that <i>T. sparrmanii</i> in Molepo Dam exhibited allometric growth, as evidenced by a strong correlation between length and weight represented by a high "r" value. This fish is in good condition because it has no competition for food due to ecological factors.

Evaluation of the toxic metals, proximate composition and length-weight relationships of selected fish species from the Gadananathi River, Southern Tamil Nadu.

The present study reveals toxic metals, proximate composition, and growth conditions in seven fish species, aiding their nutritional importance and conditions. The samples of seven different small indigenous fish species, including Xenentodon cancila, Glossogobious giuris, Pseudambassis ranga, Puntius dorsolis, Mystus vittatus, Dawkinsia filamentosa, and Dawkinsia tambraparaniei, were collected in river Gadananathi, Tamilnadu, India. A total 14 fish samples were analyzed for lead, cadmium, and copper using atomic absorption spectrometry. The standard procedures were used to determine the length-weight and proximate composition of the seven fishes. The findings revealed that the seven fish species had variable amounts of metal buildup. Cu levels were highest in D. tambraparniei gills and lowest in M. vittatus gills and livers; nonetheless, substantial amounts of Cu were found in P. dorsalis livers. In the length-weight correlations of the regression parameters of coefficient value r2, the "a" and "b" values revealed a positive allometric growth rate in all fish species except G. giuris and M. vittatus. However, X. cancila had the highest composition in the proximate analysis, while D. tambraparniei and D. filamentosa had the highest protein content mean value at a significant level (P ≤ 0.05). Overall, discrepancies in nutritional content might be related to species, environmental circumstances, fish age and size, and food availability.

Determination of Growth Indicators for Cyprinus carpio (Linnaeus, 1758) in Anzali Lagoon, Iran.

<b>Background and Objective:</b> Understanding the biology of fish is crucial for ensuring the sustainable management and conservation of their biodiversity. The objective of this study was to observe the condition factors and length-weight relationships of <i>Cyprinus carpio</i>, which can provide valuable insights into the ecological and nutritional conditions of aquatic animals. <b>Materials and Methods:</b> Condition factor (CF) and length-weight relationship (LWR) for 100 specimens of <i>C. carpio</i> collected from the Anzali Lagoon 2016 (April to August) were studied. To determine the size of each fish, the total length using a caliper with a precision of 0.1 mm and the weight using a balance with an accuracy of 0.1 g was measured. Differences were analyzed using ANOVA with the Tukey's <i>post hoc</i> test. In order to evaluate the differences in sexes each month, a non-parametric Chi-square test was employed. <b>Results:</b> The total length and body weight of <i>C. carpio</i> ranged from 9.1-53.8 cm and 110.3-5565.2 g, respectively. It was observed that there is a strong positive correlation between length and weight (r = 0.96). The results revealed they had a negative allometry growing rate. In the condition factors, there were no significant differences between male and female specimens (p>0.05). The observed sex ratio suggests no significant difference between males and females (p>0.05). <b>Conclusion:</b> The Anzali Lagoon population of <i>C. carpio</i> exhibited allometric growth, as evidenced by a strong correlation between length and weight represented by a high "r" value.

Determination of the growth performance and reproductive season of wild Channa lucius (Cuvier, 1831) populations of genus Channa (Channidae, Perciformes) in the Mekong Delta, Vietnam.

This study aimed to investigate the growth and spawning characteristics of wild Channa lucius (Cuvier, 1831) populations in the Mekong Delta, Vietnam. The study was carried out from March 2011 to February 2012. The length-weight relationship of C. lucius was determined according to the equations W = 0.0044L3.2494 , R2  = 0.9157 (female fish) and W = 0.0047L3.2178 , R2  = 0.9434 (male fish). The length and weight of the body for female fish ranged from 16.3 to 36.0 cm and 49.0 to 550.0 g, and for male fish, from 14.6 to 38.2 cm and 46.0 to 639.0 g, respectively. Female and male fish had almost similar lengths at first maturity (21.3958 cm for females and 21.3952 cm for males). The condition factor of female fish ranged from 0.842 to 0.864 and for male fish ranged from 0.848 to 0.874. The gonadosomatic index of female fish was highest in June (1.68%) and lowest in November (0.69%); that of male fish was highest in June (0.53%) and lowest in September (0.15%). The sexual maturity rate (SMR) of female fish peaked in May, with SMRs of 33.3% (stage III) and 58.3% (stage IV). In conclusion, C. lucius has a positive allometric range (b > 3), reaching sexual maturity when its length reaches 21.39 cm for both sexes, and the spawning season begins in December but peaks in May and June.

Length-weight relationship: eight species of Cyprinidae from river Panjkora, Khyber Pakhtunkhwa, Pakistan / Relação peso-comprimento: oito espécies de Cyprinidae do rio Panjkora, Khyber Pakhtunkhwa, Paquistão

Abstract Seven hundred and twenty four fish specimens were captured from March to September 2016. The materials used in the current study were cast nets, hand nets. Eight cyprinid fish species were studied for their length-weight relationships. Parameter b in the LWR was 3.03, 3.06, 3.02, 2.29, 2.82, 3.43, 2.73 and 2.47 for Schizothorax plagiostomus, Schizothorax esocinus, Racoma labiata, Tor putitora, Barilius vagra, Garra gotyla, Puntius ticto and Arassius auratus respectively. Current study is the first attempt on the LWRs of cyprinid species, provide a baseline approach for conservation and /management of local fish fauna of economic importance.

Resumo Um total de 724 espécimes de peixes foi capturado de março a setembro de 2016. Os materiais usados ​​no presente estudo foram redes de lançamento, redes de mão. Oito espécies de peixes ciprinídeos foram estudadas quanto às suas relações peso/comprimento. O parâmetro b no LWR foi 3,03, 3,06, 3,02, 2,29, 2,82, 3,43, 2,73 e 2,47 para Schizothorax plagiostomus, Schizothorax esocinus, Racoma labiata, Tor putitora, Barilius vagra, Garra gotyla, Puntius ticto e Arassius auratus respectivamente. O estudo atual é a primeira tentativa sobre os LWRs de espécies de ciprinídeos, fornecendo uma abordagem de base para a conservação e o manejo da ictiofauna local de importância econômica.

Length-weight relationship: eight species of Cyprinidae from river Panjkora, Khyber Pakhtunkhwa, Pakistan / Relação peso-comprimento: oito espécies de Cyprinidae do rio Panjkora, Khyber Pakhtunkhwa, Paquistão

Seven hundred and twenty four fish specimens were captured from March to September 2016. The materials used in the current study were cast nets, hand nets. Eight cyprinid fish species were studied for their length weight relationships. Parameter b in the LWR was 3.03, 3.06, 3.02, 2.29, 2.82, 3.43, 2.73 and 2.47 for Schizothorax plagiostomus, Schizothorax esocinus, Racoma labiata, Tor putitora, Barilius vagra, Garra gotyla, Puntius ticto and Arassius auratus respectively. Current study is the first attempt on the LWRs of cyprinid species, provide a baseline approach for conservation and /management of local fish fauna of economic importance.

Um total de 724 espécimes de peixes foi capturado de março a setembro de 2016. Os materiais usados no presente estudo foram redes de lançamento, redes de mão. Oito espécies de peixes ciprinídeos foram estudadas quanto às suas relações peso/comprimento. O parâmetro b no LWR foi 3,03, 3,06, 3,02, 2,29, 2,82, 3,43, 2,73 e 2,47 para Schizothorax plagiostomus, Schizothorax esocinus, Racoma labiata, Tor putitora, Barilius vagra, Garra gotyla, Puntius ticto e Arassius auratus respectivamente. O estudo atual é a primeira tentativa sobre os LWRs de espécies de ciprinídeos, fornecendo uma abordagem de base para a conservação e o manejo da ictiofauna local de importância econômica.

Length-weight relationship: eight species of Cyprinidae from river Panjkora, Khyber Pakhtunkhwa, Pakistan

Abstract Seven hundred and twenty four fish specimens were captured from March to September 2016. The materials used in the current study were cast nets, hand nets. Eight cyprinid fish species were studied for their length-weight relationships. Parameter b in the LWR was 3.03, 3.06, 3.02, 2.29, 2.82, 3.43, 2.73 and 2.47 for Schizothorax plagiostomus, Schizothorax esocinus, Racoma labiata, Tor putitora, Barilius vagra, Garra gotyla, Puntius ticto and Arassius auratus respectively. Current study is the first attempt on the LWRs of cyprinid species, provide a baseline approach for conservation and /management of local fish fauna of economic importance.

Resumo Um total de 724 espécimes de peixes foi capturado de março a setembro de 2016. Os materiais usados no presente estudo foram redes de lançamento, redes de mão. Oito espécies de peixes ciprinídeos foram estudadas quanto às suas relações peso/comprimento. O parâmetro b no LWR foi 3,03, 3,06, 3,02, 2,29, 2,82, 3,43, 2,73 e 2,47 para Schizothorax plagiostomus, Schizothorax esocinus, Racoma labiata, Tor putitora, Barilius vagra, Garra gotyla, Puntius ticto e Arassius auratus respectivamente. O estudo atual é a primeira tentativa sobre os LWRs de espécies de ciprinídeos, fornecendo uma abordagem de base para a conservação e o manejo da ictiofauna local de importância econômica.

Variations in length-weight relationship, growth and body condition of the commercial mullet Ellochelon vaigiensis in the Vietnamese Mekong Delta.

The Squaretail mullet Ellochelon vaigiensis is widely found from marine to brackish and freshwater, including the Vietnamese Mekong Delta (VMD). Data on the length-weight relationships (LWRs), growth pattern, and condition factor (CF) play an essential role in fisheries assessment but are limited to E. vaigiensis - a commercial fish in VMD. To better understand the growth pattern of this fish, the study collected samples at four sites, including Thanh Phu, Ben Tre (BT); Duyen Hai, Tra Vinh (TV); Tran De, Soc Trang (ST); and Dong Hai, Bac Lieu (BL). Each month, fish samples were collected using bottom nets at each sampling site during high tide in both the dry season (January to May 2021) and the wet season (November to December 2020 and June to October 2021). This study qualified whether LWRs, growth pattern, and CF of E. vaigiensis vary with sexual, intraspecific, and spatiotemporal variables. The analysis results of 942 specimens showed that fish total length (TL = 17.86 ± 0.13 cm) and weight (W = 54.29 ± 1.05 g) changed with sex, season, month and site. The W could be appraised from a given TL due to high coefficients (r 2 ) of LWRs that were regulated by fish size and season but not sex. The species showed negative allometry as its slope value of LWRs (b = 2.34 ± 0.30) was <3. The growth pattern did not change with sex and site but varied fish size, season, and months ranging from negative allometry to isometry. The CF of females (1.08 ± 0.01) was higher than males (0.99 ± 0.01). Albeit this fish showed spatiotemporal variation in CF, ranging from 0.81 ± 0.01 to 1.25 ± 0.02, the CF (1.02 ± 0.01) was significantly higher than the one threshold, indicating that E. vaigiensis lived a favorable condition. Research results show that this fish species has a dominant growth pattern in terms of length (b < 3) and is well adapted to the environment (CF ≈ 1). These data have an important role in suggesting the future aquaculture of this fish.

Condition Factor and Length-Weight Relationship of Scardinius erythrophthalmus (Linnaeus, 1758) in Anzali Lagoon.

<b>Background and Objective:</b> Studies on fish biology are essential for the sustainable management and conservation of fish biodiversity. This study observed the length-weight relationships and condition factors of common rudd fish, which give us some information about the ecological and nutritional conditions of fish. This information is crucial to fishery management. <b>Materials and Methods:</b> The length-weight relationship (LWR) and condition factors (K) of 270 <i>Scardinius erythrophthalmus</i> caught in Anzali Lagoon from April to August, 2015. <b>Results:</b> The total length and body weight of <i>S. erythrophthalmus</i> ranged from 94-179 mm and 11.98-98.5 g, respectively. A strong positive relationship was observed between length and weight (r = 0.96). There were no significant differences in the condition factors of males and females (p>0.05). The lowest K value was observed in April (K = 1.5±0.04) and the highest in July (K = 2.25±0.34). The sex ratio of 1.0 male: 1.15 female was observed, with no significant difference between males and females (p>0.05). <b>Conclusion:</b> In this study, the regression coefficient (b) in males and females was 3.35 and 3.29, respectively, more than 3.0, which means they have positive allometry growth in both sexes.

Monthly variations in growth pattern and condition factor of Periophthalmodon septemradiatus (Gobiiformes: Periophthalminae) living along the Bassac River in Viet Nam.

Periophthalmodon septemradiatus (Hamilton, 1822) is a unique mudskipper living in the mudbanks from estuarine to riverine regions in the Vietnamese Mekong Delta (VMD), but there is no data on its growth patterns and condition factors that are helpful for fish resource assessment and adaptation understanding. This study was conducted at five sites, from the lower (Soc Trang province) to middle (Can Tho city) and upper (An Giang province) reaches of Bassac River in VMD, to provide knowledge on growth patterns and condition factors to this mudskippers. Fish samples were caught using traps and hands for 24 months, from July 2017 to June 2019, at these five sites. The total length and weight of 3,417 individuals (1,340 females and 2,077 males) varied by sex, season and site (p < 0.001 for all cases). This species exhibited a positive allometric type as the slope (b = 3.06 ± 0.01) of the length-weight relationship (LWR) was >3 (p < 0.001) for both sexes. The growth pattern changed with sex as mudskipper showed isometry in females but positive allometry in males. Maturity also affected fish growth type since it shifted from negative allometry in immature groups to positive allometry in mature groups. The growth pattern of fish changed from isometry in the dry season to positive allometry in the wet season. The mudskipper showed isometry at the lower reaches in Soc Trang but positive allometry at the middle and upper reaches in Can Tho and An Giang. The condition factor (CF) did not change according to sex, size and season, but with month and site variables. The present environmental condition in these studied sites tended to be not good enough for this fish as CF (0.95 ± 0.01) was less than 1 (p < 0.001). The findings provided basic information on the growth and adaptation of P. septemradiatus being helpful in fish adaptation understanding and resource conservation in VMD.

[Growth heterogeneity of Larimichthys polyactis in spring and autumn along the coast of Zhejiang, China]. / 浙江沿岸春秋季小黄鱼生长异质性.

In order to understand the growth dynamics of Larimichthys polyactis in spring and autumn along the coast of Zhejiang Province, we used the survey data of bottom trawlers in spring (April) and autumn (November) from 2014 to 2019 along the coast of Zhejiang Province to examine the heterogeneity of L. polyactis growth by constructing a generalized linear model (GLM) and nine linear mixed effect models (LMEM). The results showed that body length of L. polyactis ranged from 15 mm to 210 mm, with an average of 124.12 mm. The dominant body length group ranged from 110 mm to 140 mm. The body weight ranged from 0.04 g to 156.2 g, with an average of 33.28 g. The dominant body weight group ranged from 30 to 50 g. According to the AIC minimum criterion, the LMEM model with the random effects of seasons and water zones on growth parameters a and b was the best. The results of cross validation also showed that the prediction of this model was the best. In the optimal model, the fixed value of growth parameter a was 0.61×10-4, which ranged in (0.32-1.91)×10-4 after adding season and water random effect. The fixed value of parameter b was 2.73, and ranged from 2.49 to 2.86 after adding the random effects of season and water area, indicating that small yellow croaker was under negative allometric growth. Season and water zone had significant effects on the relationship between body length and body weight of small yellow croaker. From a seasonal perspective, the growth rate of small yellow croaker in spring was higher than that in autumn. From water zone perspective, the closer the offshore distance, the faster the growth rate of small yellow croaker.

Data on length-weight and length-length relationships, mean condition factor, and gonadosomatic index of Rutilus rutilus and Perca fluviatilis from the Ob River basin, Western Siberia.

Raw data were obtained from 250 specimens of roach Rutilus rutilus and 274 specimens of perch Perca fluviatilis at 15 sampling sites located from North to South Taiga. Fish sampling was performed using gill-nets with 22 and 28 mm mesh. Total and eviscerated weights, total and standard lengths, fish sex, gonad weight and maturity stage were recorded. Linear regression analysis of log-transformed total weight and total length values was performed. Regression slope and intercept were used to obtain length-weight relationships and mean condition factor values. Length-length relationships were calculated by the linear regression between the total and standard lengths. Gonadosomatic index was determined using the gonad weight and the total weight of fish. The data are useful for establishing biomass, fish growth patterns, relative condition of individuals within a sample or across populations.

A review of giants: Examining the species identities of the world's heaviest extant bony fishes (ocean sunfishes, family Molidae).

The world's heaviest extant bony fish has long been considered the ocean sunfish Mola mola (family Molidae). However, recent taxonomic research suggests the world record specimen (2300 kg) was actually a misidentified giant sunfish M. alexandrini. Moreover, the history of taxonomic confusion in the genus Mola, combined with anecdotal size information perpetuated in both media and literature, has resulted in uncertainty in regard to species identity and actual weights of very large Mola specimens. In this study, we searched for records of molid specimens with reported body mass over 2000 kg, with a focus on the north-west and south-west Pacific. For each specimen, we reviewed the species identification and assessed the reliability of the information, including if the specimen had actually been weighed. Of the 15 specimens uncovered, we identified one M. mola and 14 M. alexandrini, and found that only five had actually been weighed (one with the viscera removed). Furthermore, we collected length-weight data for verified M. alexandrini specimens from the literature and museum specimens, and established the first length-weight relationship for this species [body mass (kg) = 1.1 × 10-5 × total length (cm)3.3248 (29-330 cm total length, n = 20)]. These findings are discussed in the context of other extant bony fish species, which allegedly also exceed 2000 kg in body mass, i.e., other Molidae species and the beluga sturgeon Huso huso. Overall, we conclude that M. alexandrini is the only extant bony fish species we could confirm that exceeds 2000 kg, and that basic biological information is generally not collected when very large molid specimens occasionally are stranded or are caught. Finally, we confirm that the world's heaviest extant bony fish specimen actually weighed was a female M. alexandrini (2300 kg, 272 cm total length) captured from Kamogawa, Chiba Prefecture, Japan, on August 16, 1996.

[Heterogeneity of fork length-weight relationship for juvenile Engraulis japonius based on linear mixed-effects models]. / 基于线性混合效应模型的日本鳀幼鱼叉长-ä½“é‡å ³ç³»å¼‚è´¨æ€§.

In order to examine the growth heterogeneity of juvenile Engraulis japonicus, we conducted heterogeneity analysis of fork length-weight relationships of the species based on the samples of juvenile E. japonius from April to June 2019 collected from the coastal waters of Zhejiang Province by using the generalized linear model and 9 linear mixed-effect models. The results showed that the fork length of juvenile E. japonius was between 14-74 mm, with an average of 33 mm. The dominant fork length group was 21-50 mm. The weight range was 0.01-2.96 g, with an average of 0.28 g, and the dominant body weight group was 0.01-0.50 g. According to Akaike information criterion (AIC), the growth-fitting model with both months and regions random effects on the growth parameters a and b of juvenile E. japonius fitted best.The reliable prediction results was testified by the cross-validation. In the best model, the fixed value of growth parameter a was 0.24×10-5 and its estimated value did not fluctuate significantly, while the fixed value of b was 3.246 and the estimated value ranged from 3.206 to 3.272, indicating that juvenile E. japonius was under positive allometric growth. Our results suggested that month and region significantly affected the fork length-weight relationships of juvenile E. japonius.

Batoid Abundances, Spatial Distribution, and Life History Traits in the Strait of Sicily (Central Mediterranean Sea): Bridging a Knowledge Gap through Three Decades of Survey.

Batoid species play a key role in marine ecosystems but unfortunately they have globally declined over the last decades. Given the paucity of information, abundance data and the main life history traits for batoids, obtained through about three decades of bottom trawl surveys, are presented and discussed. The surveys were carried out in two areas of the Central Mediterranean (South of Sicily and Malta Island), in a timeframe ranging from 1990 to 2018. Excluding some batoids, the abundance trends were stable or increasing. Only R. clavata, R. miraletus, and D. oxyrinchus showed occurrence and abundance indexes notable enough to carry out more detailed analysis. In particular, spatial distribution analysis of these species highlighted the presence of two main hotspots in Sicilian waters whereas they seem more widespread in Malta. The lengths at first maturity (L50) were 695 and 860, 635 and 574, and 364 and 349 mm total length (TL), respectively, for females and males of D. oxyrinchus, R. clavata, and R. miraletus. The asymptotic lengths (L∞) and the curvature coefficients (K) were 1365 and 1240 (K = 0.11 and 0.26), 1260 and 1100 (K = 0.16 and 0.26), and 840 and 800 mm TL (K = 0.36 and 0.41), respectively, for females and males of D. oxyrinchus, R. clavata, and R. miraletus. The lack of detailed quantitative historical information on batoids of Sicily and Malta does not allow to analytically judge the current status of the stocks, although the higher abundance of some species within Malta raises some concern for the Sicilian counterpart. In conclusion, suitable actions to protect batoids in the investigated area are recommended.

Seasonal dynamics of mesozooplankton biomass over a sub-Arctic continental shelf.

Mesozooplankton research in high latitude ecosystems tends to focus on different life stages of Calanus spp. due to its biomass dominance and trophic roles. However, a complex seasonal succession of abundant smaller mesozooplankton taxa suggests that the ecological functioning of the mesozooplankton communities is more complicated. We studied the year-round taxon-specific biomass measurements and size distributions of mesozooplankton on a sub-Arctic continental shelf based on formalin preserved samples. Our results confirm that Calanus spp. dominate the mesozooplankton biomass (81%). We show that commonly used length-weight relationships underestimate Calanus biomass in autumn and winter, and accordingly, a strong seasonal bias was introduced in our understanding of sub-Arctic plankton communities. We observed two periods with considerable contribution of meroplankton, the planktonic larvae of benthic invertebrates, to the mesozooplankton biomass: (a) Cirripedia nauplii accounted for 17% of total biomass close to the coast in early April and (b) meroplankton comprised up to 12.7% of total biomass in late July. Based on these results, we suggest that meroplankton may play an ecologically important role in addition to their role in dispersal of benthic species. We conclude that the seasonal succession of the biomass of small-sized holoplankton and meroplankton, often obscured by patterns in the Calanus biomass, should receive more attention as these smaller individuals are likely an important functional component of the pelagic food web.

Fillet Yield and Length-Weight Relationship of Five Fish Species From Lower Benue River, Makurdi, Nigeria.

The body characteristics and yield indices of Clarias gariepinus, Bagrus bajad, Synodontis nigrita, Labeo senegalensis and Mormyrus rume from lower Benue River in Nigeria were determined in this study using 60 samples each for the fish species. Length, weight and fillet correlations were also determined during the study. Results obtained showed that M. rume, L. senegalensis and C. gariepinus had the highest percentage of edible parts (≥ 55%) compared to the other species (≤ 39%). Concerning correlations of the fillet with the morphological variables, results obtained suggest that fillet yield is independent of fish size (except for C. gariepinus which was positively correlated). Also, only samples of L. senegalensis showed isometric growth pattern; the other fish species had either positive (C. gariepinus and B. bajad) or negative (S. nigrita and M. rume) allometric growth. While the difference in fillet yield and body characteristics was attributed to the structural anatomy and other biological dynamics of the fishes, this study could not establish a connection between fillet yield and the length-weight relationship. It was concluded that M. rume, L. senegalensis and C. gariepinus would be better export products because of their higher fillet yields.

Using model selection to choose a size-based condition index that is consistent with operational welfare indicators.

Quantitative and qualitative measures of fish health and welfare are essential for management of both wild capture and aquaculture species. These measures include morphometric body condition indices, energetic condition and aquaculture operational welfare indicators (OWIs). Measures vary in ease of measurement (and may require destructive sampling), and it is critical to know how well they correlate with fish health and welfare so appropriate management decisions can be based on them. Lumpfish (Cyclopterus lumpus) is a new farming species that needs nondestructive OWIs to be developed and validated. In this study, we developed a C. lumpus fin damage score. Four different body condition indexes based on individual weight relative to either length-weight relationships or relative to other fish in its local environment were tested (using model selection) as predictors of individual fin damage. Results showed severity of fin damage was predicted by small size relative to the other individuals in the tank or cage. Body condition based on length-weight relationship was not found to predict fin damage, indicating that using established indices from fisheries or from other species would not predict welfare risks from fin damage. Implications are that especially in hatchery conditions grading will improve the condition index, and is expected to mitigate fin damage, but that low weight at length was not of use in predicting fin damage. Model selection to choose between a suite of possible indices proved powerful and should be considered in other applications where an easily measured index is needed to correlate with other health measures.