Length-weight Regressions Research Articles

English

The ultimate objective of this study was, to explore community structure and biomass of zooplankton in relation to key environmental drivers to bear out the productivity of Lake Tinishu Abaya. Zooplankton samples collection was carried out for a year from January to December 2016 from two sampling sites (open and shore) using 30 µm mesh size net within the euphotic depth. Biomass of zooplankton was anticipated using length-weight regressions adjusted for the representative microcrustacean and biovolume of Rotifera from linear dimensions applied to simple geometric formula appropriate to body shape. In parallel, in-situ and laboratory measurements of the various physicochemical factors were performed using the standardized method. The results of the present study are given strongly generalized that Rotifera had the highest number of species (11 species) followed by Cladocera (5 species) and Copepods (2 species). Diversity parameter, the Shannon diversity index was higher for Rotifera (2.45) than cladocerans (2.395) and copepods (2.384). The mean total biomass of copepods, cladocerans, and Rotifera were 174.4, 46.76 and 13.67 µg/L at open site and 101.8, 51.35 and 10.9 µg/L at shore site, respectively. Physicochemical factors responsible for the observed variations in the biological features of the lake generalized that the lake water was fresh, well oxygenated, slightly warm, alkaline, very turbid, and with relatively high inorganic nutrients. The presence of fairly high diversity, abundance, and biomass of zooplankton in the study shows that the ecosystem of Lake Tinishu Abaya is chemically, physically and biologically productive which supports most of the aquatic life. Key words: Biomass, community structure, Lake Tinishu Abaya, productive, zooplankton

Development and sexual dimorphism of the sonic system in three deep-sea neobythitine fishes and comparisons between upper mid and lower continental slope

Based on morphology, NB Marshall identified cusk-eels (family Ophidiidae) as one of the chief sound-producing groups on the continental slope. Due to food scarcity, we hypothesized that sonic systems will be reduced at great depths despite their potential importance in sexual reproduction. We examined this hypothesis in the cusk-eel subfamily Neobythitinae by comparing sonic morphology in Atlantic species from the upper-mid (Dicrolene intronigra) and deeper continental slope (Porogadus miles and Bathyonus pectoralis) with three Taiwanese species previously described from the upper slope (Hoplobrotula armatus, Neobythites longipes and N. unimaculatus). In all six species, medial muscles are heavier in males than in females. Dicrolene has four pairs of sonic muscles similar to the shallow Pacific species, suggesting neobythitine sonic anatomy is conservative and sufficient food exists to maintain a well-developed system at depths exceeding 1km. The sonic system in Porogadus and Bathyonus was reduced to a single pair of ventral medial muscles that connects to a smaller and thinner swimbladder via a long tendon. Small muscle fiber diameters, a likely indicator of rapid contraction, were present in males of five of the species. However, in Bathyonus, the deepest species (pale coloration, reduced eye size, shorter sonic muscles and longer tendons), muscle fibers were larger suggesting an adaptation to facilitate rapid bladder movement for sound production while using slower contractions and less metabolic energy. The six species separate into three groups in length-weight regressions: the three upper slope species have the greatest weights per unit length, Dicrolene is lower, and the two deep species are further reduced consistent with the hypothesis that food limitation affects sonic anatomy at great depths.

Length-weight Relationships and Chemical Composition of the Dominant Mesozooplankton Taxa/species in the Subarctic Pacific, with Special Reference to the Effect of Lipid Accumulation in Copepoda.

Asami Nakamura, Kohei Matsuno, Yoshiyuki Abe, Hiroshi Shimada, and Atsushi Yamaguchi (2017) While length-weight (L-W) regressions for warm-water zooplankton taxa from the waters neighbouring Japan already exist, they are still missing for comparable cold-water species. In this study, the L-W regressions of 41 species belonging to 12 taxa that are dominant in the Oyashio region were reported. The body length and volume of zooplankton were measured with an image-analysis system, and the effects of lipid accumulation in Copepoda on their mass and chemical composition were quantified. The L-W regressions had a high coefficient of determination (mean r2 = 0.886). For the chemical composition, the water composition ranged from 69.8 to 95.2% wet mass (WM), carbon (C) composition from 3.8 to 60.8% dry mass (DM) and nitrogen (N) composition from 1.0 to 10.1% DM. Taxon-specific differences in the chemical composition were marked for the gelatinous taxa (Appendicularia, Cnidaria, Salpida), which also had high water and low C composition. Because C is an index of lipids, high water compositions together with low lipid compositions are considered to be characteristics of the gelatinous taxa. The most significant effects of lipid accumulation in the Copepoda are changes in DM and C. Within the same developmental stage, the DM and C compositions of the full lipid-containing specimens showed 495% and 741% increases, respectively, over those of the low lipid-containing specimens. These differences exceeded the changes after moulting (78.1%) for general copepod species. Thus, lipid accumulation should be evaluated for the accurate mass estimation of boreal Copepoda by image analysis.

Length-weight relationship and condition factor of Tilapia guineensis from Bodo City fish landing site Rivers State, Nigeria

The length- weight relationship and condition factor of Tilapia guineensis from Bodo city fish landing site, Rivers State, Nigeria, was carried out. Sampling was done fortnightly for a period of four months (March–June, 2016). The length-weight regression statistics was done using a software known as FISAT (Fish Stock Assessment Tool). The result obtained indicated that the water quality parameters were within the range favourable for the growth of the fish. Also, T. guineensis exhibited sexual dimorphism with sex ratio of 1.2:1.0 which was significantly biased in favour of the females. The length-weight relationship showed negative allometric growth, with b= 2.01. Moreover, T. guineensis had a very high condition factor which ranged between 2.03-2.32 in both male and female fish, which is an indication of the well-being of the species in this environment.Keywords: Length-Weight, condition factor, tilapia, Bodo Creek

Length-weight relationships for 48 fish species of the Gediz estuary, in İzmir Bay (Central Aegean Sea, Turkey)

Length-weight relationships were calculated for 48 fish species from İzmir Bay in the Aegean Sea, Turkey. A total of 3584 fish specimens were captured with beach seine, handline, fyke net, scoop net, castnet and trammel net in 2010–2014. The sample size ranged from three individuals for Squatina squatina to 140 for Mugil cephalus. R2 values varied between 0.95 for Pomatoschistus bathi and 0.99 for Argyrosomus regius, Chelon labrosus and Mugil cephalus. All regressions were highly significant (P < 0.001). Values of the exponent b in the length-weight regression (W = aLb) ranged from 2.750 for S. squatina to 3.514 for Syngnathus acus and the median value was 3.134 with 25–75% of the values ranging between 3.030 and 3.218.

Infestation of Pseudione tuberculata (Isopoda: Bopyridae) on juveniles of Lithodes santolla (Magellan region, Chile): a spatial mesoscale analysis

We document latitudinal patterns of infestation of the bopyrid parasite isopod Pseudione tuberculata on southern king crab Lithodes santolla juveniles (20-77 mm carapace length) recruited to fishing grounds in the southern Chilean fjord system. Seven hundred and fifty individuals were collected by semiautonomous diving in 11 of 21 sampling locations in the study area, along the western margin of the Magellan region between August and October 2013.The prevalence of P. tuberculata varied between 0 and ~22%, and displayed a spatial pattern associated with three areas: i) northern Beagle Channel (10 to ~22%; lengths between 37 and 47 mm), ii) northwestern Navarino Island without infestations (0%; 26-55 mm), and iii) Piazzi Island-Capitan Aracena Island (0-12%; 50-77 mm). Infestations were independent of host sex, while parasite prevalence decreased with host length. No parasites were observed on crabs longer than 60 mm. A comparison of slopes between linearized length-weight regressions suggests that parasitized individuals had lower weight growth than uninfested individuals. Both southern king crab juvenile density and P. tuberculata prevalence were higher in fishing areas towards Beagle Channel where previous research reported lower average surface water temperatures ( 30). The study area covers five zones relevant for the conservation and protection of sub Antarctic biodiversity, and provides opportunities for large-scale geographic studies of the host-parasite relationship

Influence of hydrology on the fish body condition in a large subtropical floodplain

ABSTRACT With the objective of finding fluctuations on fish body condition in the Middle Paraná River floodplain in different hydrological scenarios, this attribute was analyzed in several trophic groups of a secondary floodplain channel and its associated lakes between 2010 and 2012. Standardized residuals generated by length-weight regressions were calculated for each species and the relative weight (Wr) of the most abundant species per group was examined. A two-way factorial ANOVA was carried out (factors: hydrology and habitats) to evaluate the existence of significant spatial-temporal differences by groups and species. Results showed that body condition in detritivorous, herbivorous and omnivorous species fluctuated significantly depending on hydrology and the environment. Optimal body condition was recorded after the largest flood pulse in most species. Body condition decreased during the low-water period and after two disconnection periods, whereas during the second flood pulse it increased in detritivores, herbivores and omnivores. No floods occurred thereafter, but two flow pulses were registered, and body condition increased under these hydrologic scenarios, with similar or higher values to those recorded after the largest pulse. These results indicate that flow pulses, which are supplementary to flood pulses, may have a positive effect on fish body condition.

Lenght-weight relationship and condition factof of Leuciscus niloticus (De Joahhis 1853) from Epe Lagoon, Lagos State, Nigeria

Leuciscus niloticus samples were obtained from Epe lagoon, Lagos state, Nigeria. The fish samples were designated into pooled, male and female sex respectively. Length-weight relationship was carried out to investigate the correlation value, growth pattern and the condition factor (k) of pooled, male and female Leuciscus niloticus . In this study, the growth pattern of pooled, male and female Leuciscus niloticus from Epe lagoon shows that the “b” values were 2.56, 2.62 and 2.38 respectively, showing that all the fish sampled exhibited negative allometric growth pattern. The overall length weight regression equation for pooled was (Log W = -1.679 + 2.559 log TL), (r = 0.898), and also the length-weight equations of males and females (Log W = -1.759 + 2.618 log TL) (r=0.919), (Log W = -1.449 + 2.384 log TL) (r=0.870) respectively. The mean condition factor (k) of Leuciscus niloticus was 0.55 ± 0.08 for pooled, 0.54 ± 0.08 and 0.55 ± 0.09 for both male and female respectively indicate poor adaptation of the fish in the Epe lagoon.

Morphometric variation of Parapocryptes serperaster (Gobiidae) in dry and wet seasons in the Mekong Delta, Vietnam

Parapocryptes serperaster is a bottom-dwelling goby species widely distributed throughout monsoonal regions in Asia. A year-round study (2013–2014) on the length–weight relationship and body shape of this goby was conducted in the Mekong Delta, Vietnam, to understand its morphometric change and growth characteristics during the wet (January–May) and dry (June–December) seasons. The sex ratio in all collected specimens was not significantly different between wet and dry seasons. The female P. serperaster weighed (7.2–54.5 g) more than the males (6.7–49.0 g), but female length (12.5–21.2 cm) was not different from males (12.5–23.0 cm). Length–weight relationships were similar between female and male P. serperaster. Male and female fish showed a similar growth pattern between wet and dry seasons and the slope of the length–weight regression was close to the standard value (b = 3) for isometric growth. The body condition factor decreased as fish grew, but the seasonal impact on the condition factor depended on gender. The condition factor of male P. serperaster was greater than that of females in the wet season, but not significantly different between genders in the dry season. This goby shows isometric growth and provides useful information for our understanding on gobiid morphometric variation in areas with monsoonal seasonality.

Improved estimates of calanoid copepod biomass in the St. Lawrence Great Lakes

We compared measured lengths and weights of six species of calanoid copepods: Limnocalanus macrurus , Senecella calanoides , Epischura lacustris , Diaptomus sicilis , Diaptomus oregonensis , and Diaptomus minutus to weights predicted using four length–weight regression equations. Copepods were collected from multiple sites in Lakes Erie , Huron, Michigan, Ontario and Superior in 1993, 1995, 1996, 1997, 2009, or 2013. All models exhibited statistically significant failures in some cases. The Pace and Orcutt regression used by the USEPA GLNPO underestimated measured biomass, whereas models by Dumont et al. and Bottrell et al. overestimated biomass. Variability in weight at fixed body lengths was greatest for the large, univoltine species L. macrurus and S. calanoides in their C6 instars. Differences were found in weights of identical species of the same length across lakes, sampling time, and years. Disparities between predicted and observed dry mass interject error in estimates of secondary production, herbivory , planktivory , and forage availability to zooplanktivorous fish. Representative size frequency distributions of Calanoida suggest that summertime community-level Order-specific biomass has been underestimated by about 50%. The size–frequency data indicate that the dominant source of uncertainty in community biomass estimates necessarily resides with the largest taxa, which are coincidently the most inherently variable. We propose a revised equation based on Great Lakes taxa that accounts for 90% of the variance in our data overall, but we suggest that uncertainty cannot be substantially improved beyond that level if body length is the sole proxy for individual biomass estimates for copepods of the Great Lakes.

Validation of Annulus Formation in Spotted Sucker Otoliths

Abstract Spotted suckers Minytrema melanops are found in many river systems from the Midwest to the Southeast United States. Though they are a relatively abundant species, otolith age validation methods have not been reported. The objective of this study was to validate annulus formation on the lapillar otolith for spotted suckers. We collected spotted suckers monthly from December 2005 to November 2006 in the Apalachicola River, Florida. Using marginal incremental analysis on whole browned lapillar otoliths, we validated that spotted suckers form one annulus per year between May and June. We also report population characteristics including a length–weight regression. This study validates otolith aging to provide an avenue for accurately assessing the age composition of spotted sucker populations, which will facilitate a better understanding of growth, recruitment, and mortality of the species.

A comparison of gender growth performance of Procambarus clarkii (Girard, 1852) under aquaculture conditions

The red swamp crayfish, Procambarus clarkii (Girard, 1852) is one of the most commonly-farmed freshwater species in inland China, but the yield is very low. The aim of this study was to assess whether the gender has effect on growth performance of P. clarkii. Male and female juvenile crayfish were individually reared in net cages for 75 days (trial 1). In addition, juvenile crayfish and adult crayfish of different gender were group-reared for 60 days and 30 days respectively (trials 2 and 3). The weight growth rate (WGR, %), length growth rate (LGR, %) and survival rate (SR, %) were monitored. Results showed that the length-weight regressions differed significant between males and females juvenile crayfish (P females > males) was noted among monosex and mixed-sex groups. No significant difference was noted, in terms of LGR, between females and males (P>0.05). However, the LGR of each of these was significantly lower than that of the mixed-sex groups (P<0.01). Our results demonstrated the gender has some effect on growth performance of P. clarkii, especially on adult crayfish.

Population characteristics of bighead and silver carp on the northwestern front of their North American invasion

Invasive species are considered the second largest threat to native biodiversity, and ecosystem function and services. One pair of global invaders, bighead, Hypophthalmichthys nobilis, and silver carp, H. molitrix, (collectively referred to as Asian carps) have been introduced throughout the world, and are invading three prairie stream tributaries to the Missouri River in the United States. There is a paucity of knowledge and understanding about Asian carp population characteristics and biology in North America. As such, we documented spatial and temporal trends in population dynamics (i.e., density, size structure, age, growth and condition) of Asian carps in three tributaries to the Missouri River in South Dakota: Big Sioux, James and Vermillion from 2009 to 2012. Finally, native planktivore (i.e., gizzard shad, Dorosoma cepedianum, bigmouth buffalo, Ictiobus cyprinellus, and emerald shiner, Notropis atherinoides) characteristics were examined using condition (Fulton’s K). Overall, 469 silver carp and eight bighead carp were collected using boat electrofishing and mean catch-per-unit-effort of silver carp increased annually. The three rivers’ populations were similar in length frequencies. Silver carp growth was faster initially than later ages and overall was slower than Middle Mississippi River populations. Recruitment of silver carp was erratic with the 2010 year class dominating 91% of catches. Silver carp condition was also similar across rivers, seasons, and years. South Dakota silver carp populations were predicted from a length-weight regression to be lighter than the Gavins Point reach population of the Missouri River, and heavier than both the middle Mississippi and the Illinois River populations. Additionally, mean catch-per-unit-effort for bigmouth buffalo and emerald shiner decreased over the study period. Continued monitoring and research on this newly invading population of Asian carps will provide additional invaluable insight into complex invasive species, assist with understanding Asian carps population dynamics during and after an invasion, and expose the potential negative impacts Asian carps may be having on prairie stream ecosystems.

Length-weight Relationships of 30 Fish Species in Aby Lagoon, Southeastern Cote d? Ivoire

Most West African lagoons are very productive ecosystems that support important fishery activities. However, increases in human populations put heavy pressure on their resources. This raised the importance of sustainable management tools for these ecosystems. Length-Weight Relationships (LWRs) which is an important fish stock assessment tool was investigated in the Aby lagoon, southeastern Cote d'Ivoire. Fishes were caught monthly from February 2012 through March 2013 using gillnets. Fishes captured were identified, weighted to the nearest gram and standard length was measured to the nearest millimeter. The 30 fish species selected for this study belong to 18 families. The highest species number (n = 7) was recorded for Cichlidae family. All length-weight regressions were significant with a coefficient of determination (r²) varying from 0.462 (Parailia pellucida) to 0.984 (Elops lacerta). Growth coefficient, b of the LWR ranged from 2.229 (P. pellucida) to 3.811 (Eleotris vittata). Nineteen species exhibited negative allometric growth pattern while 11 had positive allometric growth. These results are useful references for West African coastal lagoon management and particularly for that of the Aby lagoon system.

Bone-to-Body Biometric Relationships for Owens and Lahontan Tui Chubs and their Hybrids in California

Abstract Regression parameters for the length of several bony structures against fish body length, and for body length against body weight, were determined for Owens tui chub Siphateles bicolor snyderi, Lahontan tui chub Siphateles bicolor obesa, and hybrid swarm deriving from the two species. Two-hundred eleven individuals from 16 localities from the Owens River and neighboring basins along the border between California and Nevada were used for regression analyses. The coefficient of determination of linear regressions for scales, pharyngeal arches, dentaries, cleithra, and opercula against body length were consistently high (r2 ≥ 0.9). Differences between subspecies were mainly with reference to the intercept parameter in comparisons involving Lahontan tui chub. Coefficients of determination from log-linear length–weight regressions were also high (r2 ≥ 0.9) for individual taxa and for the pooled data set combining both Lahontan and hybrid species. The length–weight relationship did not differ between subspecies. Estimates of the length–weight relationship using data pooling both Lahontan and hybrid tui chub suggest a weak allometric growth effect (P &amp;lt; 0.05). The bone-length to body-length and body-length to body-weight relationships presented here will be useful tools for future dietary studies of tui chub predators as well as for archaeological and paleontological studies on tui chub remains.

Historical and recent biomass and food web relations of Limnocalanus in Lake Huron

Reported population biomass of Limnocalanus macrurus in Lake Huron has been underestimated by several-fold owing to application of an inappropriate length–weight regression model. During August and September the underestimates can exceed three-fold, suggesting that secondary production of the species in the lake is greater than previously thought. Increased representation of the species in the plankton community in recent years is associated with a decrease in its trophic level deduced through nitrogen stable isotope analysis of specimens from opportunistic samples obtained in 1993, 1995, and 2009. Limnocalanus15N enrichment relative to primary herbivores appears to have decreased by 1.5‰ over this time period. Similarly, Diaptomus15N enrichment relative to primary herbivores appeared to decrease by 1.1‰ from 1993 to 2009. Our data offer at least two possible explanations for this shift. (1) Limnocalanus has adopted a more herbivorous diet in response to the ecological changes in Lake Huron or (2) hypolimnetic Diaptomus have adopted a more herbivorous diet and Limnocalanus is relying in part on Diaptomus as a food source.

Tidal Flushing Restores the Physiological Condition of Fish Residing in Degraded Salt Marshes

Roads, bridges, and dikes constructed across salt marshes can restrict tidal flow, degrade habitat quality for nekton, and facilitate invasion by non-native plants including Phragmites australis. Introduced P. australis contributes to marsh accretion and eliminates marsh surface pools thereby adversely affecting fish by reducing access to intertidal habitats essential for feeding, reproduction, and refuge. Our study assessed the condition of resident fish populations (Fundulus heteroclitus) at four tidally restricted and four tidally restored marshes in New England invaded by P. australis relative to adjacent reference salt marshes. We used physiological and morphological indicators of fish condition, including proximate body composition (% lipid, % lean dry, % water), recent daily growth rate, age class distributions, parasite prevalence, female gravidity status, length-weight regressions, and a common morphological indicator (Fulton’s K) to assess impacts to fish health. We detected a significant increase in the quantity of parasites infecting fish in tidally restricted marshes but not in those where tidal flow was restored to reduce P. australis cover. Using fish length as a covariate, we found that unparasitized, non-gravid F. heteroclitus in tidally restricted marshes had significantly reduced lipid reserves and increased lean dry (structural) mass relative to fish residing in reference marshes. Fish in tidally restored marshes were equivalent across all metrics relative to those in reference marshes indicating that habitat quality was restored via increased tidal flushing. Reference marshes adjacent to tidally restored sites contained the highest abundance of young fish (ages 0–1) while tidally restricted marshes contained the lowest. Results indicate that F. heteroclitus residing in physically and hydrologically altered marshes are at a disadvantage relative to fish in reference marshes but the effects can be reversed through ecological restoration.

Length-weight regressions of the microcrustacean species from a tropical floodplain

AIM: This study presents length-weight regressions adjusted for the most representative microcrustacean species and young stages of copepods from tropical lakes, together with a comparison of these results with estimates from the literature for tropical and temperate regions; METHODS: Samples were taken from six isolated lakes, in summer and winter, using a motorized pump and plankton net. The dry weight of each size class (for cladocerans) or developmental stage (for copepods) was measured using an electronic microbalance; RESULTS: Adjusted regressions were significant. We observed a trend of under-estimating the weights of smaller species and overestimating those of larger species, when using regressions obtained from temperate regions; CONCLUSION: We must be cautious about using pooled regressions from the literature, preferring models of similar species, or weighing the organisms and building new models.

Documenting recovery of a spawning aggregation through size frequency analysis from underwater laser calipers measurements

Many spawning aggregations of marine fishes have been fished beyond the point of sustainability, leading to increased calls for protection through seasonal and/or site-specific fishery closures. Once a closure has been put in place, monitoring the aggregation is imperative in order to learn whether protection leads to the recovery of the population. Current methods for monitoring the status of spawning aggregations rely largely on counts, either subsample or census, usually combined with capturing a subset of the fish to assess individual traits such as length and weight. Handling fish during the spawning aggregation can be stressful for the fish, and can ultimately lead to decreased spawning success, increased susceptibility to predators, or increased mortality through capture trauma or infection. Here we present a novel analysis for monitoring fish on a spawning aggregation that does not require the capture and handling of fish. Following a recovering aggregation of Nassau grouper (Epinephelus striatus) over seven spawning seasons, we show that length-distribution data can be collected by divers using a video-based system with parallel lasers calibrated to a specific distance apart, and subsequently use those data to monitor changes in the size distribution over time. We detected recruitment of new fish to the grouper spawning aggregation in the fourth year of monitoring. In addition to tracking size distribution trends over time, the length distribution information could be combined with an established length–weight regression and an estimate of total abundance to estimate spawning stock biomass. We qualitatively cross-validate this method with census data to evaluate its effectiveness in monitoring the recovery or decline of aggregating species that can be visually observed.

Influence of Cadmium Exposure on Growth and Fecundity of Freshwater Mosquitofish Gambusia affinis: In Situ and In Vivo Studies

This study aims to investigate the effect of cadmium (Cd) exposure on growth and fecundity of mosquitofish Gambusia affinis. For this purpose, two natural populations of pregnant females of G. affinis captured from two sites were differently contaminated with Cd (S1 present Cd levels 5-fold higher than S2) and a sublethal exposure to 0.4 mg CdCl(2)/L (10% of LC(50)) during 56 days was conducted in vivo. The length-weight regression revealed a significant difference in the growth between these two populations. A significant difference in fecundity was also noted between the two populations. Indeed, the embryo numbers in pregnant females captured from S1 are significantly higher than those noted in pregnant females from S2 (21.17±5 and 7.97±2.12, respectively; p<0.05). Following Cd exposure, we noted a growth perturbation resulting in lower values of both indices BWG and SGR following 7 and 21 days (-5.21 and -1.18 for BWG, and -2.09 and -0.46 for SGR, respectively) and a recuperation of growing weight at 42 and 56 days (1.32 and 1.71 for BWG, and 0.45 and 0.54 for SGR, respectively). For CF index, we observed a significant difference (p<0.05) between control and Cd groups at 7 and 21 days of exposure, and at 21 and 56 days respectively for HSI and GSI indices. Furthermore, Cd contents in both tissues (liver and yolk sac) and fractions (cytosolic and membrane) are significantly different between groups during experimentation. In addition, the Cd contents noticed in the liver membrane fraction are significantly higher than those noted in the yolk sac tissue. The MTs levels revealed a significant difference between the control and Cd groups. In liver tissue, a significant difference was noted, in MTs levels, during the Cd exposure (7, 21, 42, and 56 days) while in the yolk sac tissue the difference was noted at 42 days of exposure. Taken together, these results imply the potential negative effect of Cd on physiological status of G. affinis as evidenced by decreasing growth and fecundity rate.