Change in body size of juvenile marbled sole <Emphasis Type="Italic">Pseudopleuronectes yokohamae</Emphasis> after preservation in ethanol

We evaluated the extent of shrinkage in body size of juvenile marbled sole Pseudopleuronectes yokohamae after preservation in 70% ethanol for 6, 12, 24, or 48 h, or 4 weeks. Standard length (SL, range of the analyzed specimens: 22.82–53.01 mm) decreased by 5.6% after 12 h and body weight (BW 0.174–2.964 g) decreased 27.8% after 24 h preservation in 70% ethanol. There was no further decrease in SL or BW after 12 or 24 h of preservation, respectively. The original body size could be estimated based on the size after preservation in 70% ethanol for 4 weeks using the following equations: SL _original = 1.05 SL _preserved + 0.37 and BW _original = 1.36 BW _preserved + 0.04. The condition factor calculated using the body size of preserved individuals was 16.0 and 15.8% lower than that calculated from the original body size and the body size back-calculated using the linear regression equations described above, respectively. Thus, our data suggest that the shrinkage of body size due to preservation in ethanol can cause errors in estimation of the condition factor. Our results can be used to improve the accuracy of estimating size-related biological parameters based on juvenile marbled sole that are preserved in ethanol.     

The effects of four preservation methods on length, weight and condition factor of the clupeid Sardinella aurita Val. 1847

Formalin preservation, freezing, and salted and non‐salted smoking are often used to preserve fishes. Body proportions of fish show changes upon preservation when applying different preserving techniques; most authors report a decrease in length and some authors report changes in weight and condition factor (k). Four groups of round sardinella (Sardinella aurita) were subjected to the above treatments. Initial fork length (cm) and weight (g) ranged from 8.7 to 10.8 cm and 6.74 to 11.4 g, respectively. All fish decreased in both length and weight, with highly significant (P < 0.05) differences. Condition factor decreased in all treatments except formalin. Percentage reductions in length, weight, and condition factor were 11.0, 68.0 and 54.8% with salted smoking; 13.0, 69.3 and 53.3% with non‐salted smoking; 3.0, 14.1 and 6.7% with freezing; and 7.1, 13.3 and 108.1% with formalin preservation, respectively. Shrinkage was the least with freezing, followed by formalin, salted smoking, and non‐salted smoking preservation.     

Preserving young‐of‐the‐year Perca fluviatilis in ethanol,formalin, or in a frozen state and the consequences for measuring morphometrics

As it is often not possible to immediately analyse individuals sampled in the field, captured fish are preserved and stored for later investigation. The objective of this study was to assess the effects of various preservation methods on subsequent changes in morphometric parameters while also providing correction factors to re‐calculate the original body dimensions when sampled fish are measured at a later date. In this study, juvenile perch (Perca fluviatilis, 66.5 ± 10.2 mm total length) were measured directly after capture, then either frozen at ?20°C, preserved in 70% ethanol, or in 4% formalin. They were again measured after 24 h, 3 days, 7 days, and thereafter on a weekly basis for 8 weeks. Ethanol‐preserved perch greatly decreased length and weight; formalin preservation also led to a comparable length reduction, but increased the weight of the perch. In contrast, frozen perch showed less shrinkage and only moderate weight loss. Of the three preservation methods, freezing clearly caused the fewest distortions. Hence, freezing is recommend as the most preferable preservation method, especially in multi‐disciplinary studies on fish ecology; for all other preservation methods the correction factor over time will have to be pre‐determined for each species and size class.     

Length–weight relationship and condition factor of the Characidae matrinxã, Brycon falcatus (Müller & Troschel, 1844), in the Teles Pires River,southern Amazon

The aim of this study was to verify whether the in situ supply of soybean as a fish attractant bears any influence on the length–weight relationship and condition factor of the omnivorous fish species, Brycon falcatus. In addition, estimated was the length–weight relationship, standard and total length, condition factor, and size of B. falcatus in the spawning period in the Teles Pires River Basin. In the experimental design, rivers of the Teles Pires Basin containing soybean attractant (Verde River, Celeste River, Teles Pires River and the Tapaiuna River) were mapped. Fish were also collected from the Cristalino River, which contained no soybean attractant (treatment control). Samples were collected from August 2012 to July 2013. Length–weight relationship of B. falcatus in the Teles Pires River Basin can be obtained by the expression: Wt = 0.0091*SL^3.376, r² = .97, n = 102, and length‐length relationship: TL = 1.128*SL + 3.978, r² = .96. The condition factor of all specimens collected in the Teles Pires Basin was k = 1.055. Size at capable phase (L50) of spawning was estimated at 23 cm standard length. Results showed no significant difference in the length–weight relationship or condition factor of B. falcatus collected from rivers with or without soybean attractant. Concluded is that the in situ supply of soybean as a fish attractant does not interfere with the wellbeing of B. Falcatus in the Teles Pires River Basin.     

Effects of preservation on dry- and ash-free dry weight biomass of some common aquatic macro-invertebrates

The effect of preservation methods on dry weight (DW) and ash-free dry weight (AFDW) of Radix peregra (Gastropoda), Asellus aquaticus (Isopoda), Erpobdella octoculata (Hirudinea) and Glyptotendipes sp. (Chironomidae) was studied. Ethanol, formaldehyde, and Bouin were used as preservative. In case of preservation of macro-invertebrates in ethanol substancial changes in DW and AFDW biomass were observed. In the four different taxa the loss in DW varied between 7.2–21.9% after a 3 month preservation period in 70% ethanol. A comparatively small range in AFDW loss (16.2–19.7%) was found. Changes in DW and AFDW biomass during preservation were significantly affected by the duration of the preservation, by temperature, light conditions and the volume of the preservative. The changes in AFDW were also significantly affected by the concentration of the preservatives. Preservation in 10% formaldehyde did not cause significant changes in DW and AFDW biomass.Contribution nr. 42 of the nymphalid project.     

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.     

Weight‐length relationships and condition factor trends for thirty‐eight fish species in trawled and untrawled areas off the coast of northern Sicily (central Mediterranean Sea)

This paper reports the weight‐length relationship (WLR) for thirty‐eight fish species from the Gulf of Castellammare (NW Sicily, Mediterranean Sea). A total of 59 870 fish were collected and measured during four seasonal trawl surveys carried out in 2005 at 10 to 200 m depth. The b parameter of the WLRs ranged from 1.79 (Cepola macrophthalma) to 3.56 (Conger conger). Significant differences in both a and b values among seasons were detected for eight species. Moreover, the condition factors (as weight‐at‐length) of Merluccius merluccius and Mullus barbatus were compared in different area/year combinations characterized by the presence or absence of trawling impact. While M. barbatus showed a higher condition factor in trawled areas/years, possibly due to density‐dependent factors linked to the increased biomass in the no‐trawl area, no such link was detected in M. merluccius.     

Fluid‐preserved fishes are one solution for assessing historical change in fish trophic level

1. There are few resources available for assessing historical change in fish trophic dynamics, but specimens held in natural history collections could serve as this resource. In contemporary trophic ecology studies, trophic and source information can be obtained from compound‐specific stable isotope analysis of amino acids of nitrogen (CSIA‐AA‐N).
2. We subjected whole Sebastes ruberrimus and Clupea pallasii to formalin fixation and 70% ethanol preservation. We extracted tissue samples from each fish pre‐fixation, after each chemical change, and then in doubling time for 32–64 days once placed in the final preservative. All samples were subjected to CSIA‐AA‐N, and their glutamic acid and phenylalanine profiles and associated trophic position were examined for differences over time by species.
3. Glutamic acid and phenylalanine values were inconsistent in direction and magnitude, particularly during formalin fixation, but stabilized similarly (in 70% ethanol) among conspecifics. In some cases, the amino acid values of our final samples were significantly different than our initial pre‐preservation samples. Nonetheless, significant differences in glutamic acid, phenylalanine, and estimated trophic position were not detected among samples that were in 70% ethanol for >24 hr.
4. Our results suggest that the relative trophic position of fluid‐preserved specimens can be estimated using CSIA‐AA‐N, and CSIA‐AA‐N estimates for fluid‐preserved specimens should only be reported as relative differences. Timelines of trophic position change can be developed by comparing specimens collected at different points in time, revealing trophic information of the past and cryptic ecosystem responses.

     

The occurrence of the tapeworm Ligula intestinalis (L.), in Barbus paludinosus from a small dam in Zimbabwe

Cestode parasites were collected from Barbus paludinosus from Munwahuku Dam near Harare, Zimbabwe over a period of 13 months. Plerocercoids of Ligula intestinalis were found in 7.2% of the fish. The majority of the infected fish carried one parasite, with 3.1% having two and 1.6% with three. There was a positive correlation (r = 0.59, P < 0.05) between the weight of L. intestinalis and that of their host, but there was no significant relationship between the condition factor of the fish and the weight of the parasite, and the parasite index was low (7.97 ± 3.38) compared to previous studies in South Africa. The gonads of all infected fish were atrophied. The prevalence of L. intestinalis in B. paludinosus was high between July and September 2000 and low thereafter. There was no clear seasonal variation in the occurrence of the parasite, although the lengthy dry season might have had an effect on the prevalence.     

Physical changes in specimens of five species of Cyprinidae preserved in ethanol and frozen

Preservation in 30% ethanol and freezing to a temperature of ?20 ± 2° C is an appropriate method for measurement of fish eggs, larvae and juveniles. Egg diameter of the common carp Cyprinus carpio increased insignificantly by 1·32% after preservation compared with live size. The total length (L_T) of 1 day post‐hatching (dph) larvae as well as the standard length (LS) of 16 dph larvae of C. carpio increased significantly (2·95 and 1·50%, respectively) after preservation. Egg diameter as well as the L_T of 1 dph larvae of barbel Barbus barbus increased significantly after preservation, by 1·74 and 1·96%, respectively over their original size. The standard length (L_S) of 14 dph larvae of B. barbus as well as juveniles of B. barbus, crucian carp Carassius carassius, common nase Chondrostoma nasus and tench Tinca tinca decreased significantly after preservation (?0·56 to ?5·54%), whereas their body mass increased significantly (11·46–18·57%). Preserved eggs of C. carpio and B. barbus were hard, round and transparent. The larvae and juveniles of examined fishes, preserved in frozen ethanol, were straight, flexible and easily measurable after 60 days. Integrity of body surface and fins, as well as preservation of colours were much better in larvae or juveniles frozen and thawed only once than in specimens frozen and thawed thrice. Cooling in 30% ethanol to a temperature of 6 ± 2° C and freezing in water to a temperature of ?20 ± 2° C are not appropriate preservation methods for eggs and larvae of C. carpio (1 and 16 dph).     

Length‐weight relationship and seasonal effects of the Summer Monsoon on condition factor of Terapon jarbua (Forsskål, 1775) from the wider Gulf of Aden including Socotra Island

The present study investigates the length‐weight relationship and condition factor of populations of the Indo‐Pacific fish Terapon jarbua ( Forsskål, 1775 ) collected in the wider Gulf of Aden, notably from Socotra Island and the Hadramout coast of Yemen. This region displays a monsoon climate, with wide seasonal variations affecting estuarine habitats. A total of 620 specimens collected in estuaries and at sea were measured and weighed during field surveys carried out in 2007 and 2008 during pre‐ and post‐ South‐Western monsoon periods. The length‐weight relationship of the studied populations of Terapon jarbua was determined as W = 0.0288 × SL^2.99, with r² = 0.96 and consistent with existing data on the species from other regions. Significant seasonal differences were found in Fulton’s condition factor of Terapon jarbua.     

Weak compensatory growth makes short-term starvation an unsuitable technique to mitigate body deformities of <Emphasis Type="Italic">Tinca tinca</Emphasis> juveniles in intensive culture

Juvenile tench, Tinca tinca (L.) (initial mean weight 0.67 g) were continuously fed at high (5.0% of fish biomass) or low (2.5% of fish biomass) daily doses of a commercial formulated diet, or starved for 6 days, then fed these doses. The experiment lasted 40 days. Visible skeletal deformities occurred in fish fed the high doses, and the 6-day food deprivation mitigated the percentage of deformed fish from 37.3 to 12.1%. Deformities were associated with higher condition coefficient value. Faster growing individuals were more susceptible to body malformations within the feeding groups. No compensatory growth in body weight was observed in juveniles fed high or low doses. Lack of compensation was supported by lower carbon/nitrogen ratio in starved-re-alimented fish. Morphometric indices (condition coefficient and height/length ratio) suggested only partial compensation observed mostly during the first few days after the end of starvation. The possible mechanisms underlying this weak compensatory response in T. tinca juveniles may be associated with their slow growth rate and low oxygen consumption. Short starvation mitigates body deformities in intensively fed tench juveniles, however, this technique is not recommended in aquaculture due to their weak compensatory growth response.     

Diet spectrum of great cormorants (<Emphasis Type="Italic">Phalacrocorax carbo sinensis</Emphasis> L.) at the Donji Miholjac carp fishponds in eastern Croatia

This paper reports the results of a diet analysis from the digestive tracts of 203 great cormorants shot at the Donji Miholjac fishponds in eastern Croatia, in the period 2000–2002. Eight fish species were determined. The dominant species was common carp (Cyprinus carpio) with a relative frequency of 73.4%, followed by grass carp (Ctenopharingodon idella) (11.6%), bighead carp (Aristichthys nobilis) (7.2%), pikeperch (Sander lucioperca) (2.0%), wels catfish (Silurus glanis) (1.7%), pike (Esox lucius) (1.5%), topmouth gudgeon (Pseudorasbora parva) (1.5%) and Prussian carp (Carassius auratus gibelio) (1.1%). The diet spectrum of the great cormorants from the Donji Miholjac fishponds was in accordance with the structure of the fish population in the fishponds. The average stomach weight per bird was 244 g. When birds shot with an empty stomach were excluded, the average stomach weight increased to 286 g. The length of consumed fish ranged from 40–335 mm, with 47% of the fish belonging to the length category 100–149 mm. The study revealed no significant relationship between the weight of the consumed fish and the body weight of male and female cormorants.     

Length‐weight relationships of fishes in the Mira basin,Colombia

This study estimated the a and b parameters of the length–weight relationships of 15 fishes from the Mira and Caunapí rivers, San Andrés de Tumaco, Nariño, Colombia. The specimens were captured during four samplings periods between 2015 and 2016 using a different a combination of fishing gillnets and electrofishing. The a values ranged from 0.0002 to 0.04 and b values ranged from 2.86 to 3.6. The data presented here are tentative estimates because the fish have been weighted and measured after fixation in formalin and ethanol, however, these data are references for weight‐length relationship for 15 species, the maximum weight for the same 15, and new maximum lengths for 3 species.     

Biometric relationships between body and otolith measurements in nine demersal fishes from north‐eastern Tasmanian waters,Australia

Relationships between fish and otolith measurements were analyzed in nine demersal fishes from the north‐eastern Tasmanian waters: Foetorepus calauropomus, Trachurus declivis, Parequula melbournensis, Neosebastes scorpaenoides, Platycephalus aurimaculatus, Platycephalus bassensis, Platycephalus conatus, Lepidotrigla mulhalli and Lepidotrigla vanessa. The values of exponent b from the relationships between fish weight and fish total length, total length and otolith length, total length and otolith width, and fish weight and otolith length were estimated. All above relationships were statistically significant. The analysis of covariance (ANCOVA) was used to test the effect of the categorical factor of species in the fish length and otolith length relationship. Significant differences in fish length and otolith length relationship between species were highlighted in both gurnards and flatheads. Results from this study will provide novel information on quantitative biometric relationships between body and otolith measurements of fish species in Australian waters.     

A possible relation between growth and number of deformed vertebrae in Atlantic salmon (Salmo salar L.)

The aim of the present study was to elucidate whether vertebral deformities influence on the growth performance of salmon, and if so, at what level of severity the growth performance/welfare is affected. To do this, Atlantic salmon postsmolts were individually tagged and reared in a common seacage from January 2005 until January 2006. At the end of the experiment, dissected vertebral columns were radiographed, evaluated for vertebral deformities, and the location and type of deformity was recorded. For statistical analysis the fish were grouped according to the number of deformed (d) vertebrae (v); 0 dv (n = 173), 1–5 dv (n = 43), 6–10 dv (n = 11), 11–20 dv (n = 18) and 21–44 dv (n = 31). In fish with less than six dv, the deformities were found within the tail fin region (v 50‐58). Fish with 11–20 dv also had a high occurrence of dv within the tail region (V31‐49), and fish with more than 20 dv also had a high occurrence of dv within the caudal trunk region (V9‐30). Growth was significantly influenced by the number of dv. At the end of the experiment, fish with more than 10 dv were shorter and had a higher condition factor than normal fish, and fish with more than 20 dv were shorter, had lower weight and a higher condition factor than normal fish. In the first period in seawater (January–June) there was no detectable differences in growth (length or weight) between the groups, but the condition factor of the individuals with a high number of dv increased. In the second period (June–January), fish with more than 10 dv, had a significantly lower growth rate. This study indicate that a low occurrence of vertebral deformities have little effect on the growth performance/welfare of salmon.     

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.     

Effect of winter feeding and starvation on the growth performance of young‐of‐year (YOY) great sturgeon,Huso huso

The objective of this study was to evaluate the feeding rate of the great sturgeon (Huso huso) young of the year (YOY) and to investigate the effects of different feeding rates in maintaining the weight of fish during short periods of winter starvation. Six feeding rates of 0.2, 0.4, 0.6, 0.8, 1.0% body weight (BW) day^?1 and feeding to satiation were considered for the first experiment. Each feeding rate was randomly assigned to three replicate tanks, with continuous feeding throughout a 5‐week winter period of water temperatures below 10°C. Fifteen fish were held in each of 18 tanks with an average initial body weight of 219.6 ± 6.9 g. After 5 weeks of feeding, the best performance was observed in fish fed 1% BW day^?1, but negative growth was observed in fish fed 0.2% BW day^?1. In the second experiment, fish were deprived of feed for 3 weeks at winter temperatures. Weights and condition factors of all fish decreased during starvation, while the differences in mean weight before and after the starvation period were not significant in fish fed a level of 0.2% BW day^?1 and those fish fed to satiation. No mortality was recorded in either experiment. Results of this study indicate that a feeding rate of 1% BW day^?1 would be sufficient for commercial fish farming of YOY of this species to maintain them over winter. Also, to maintain fish weights and prevent weight loss in overwintering ponds, a feeding rate of around 0.3% BW day^?1 seems appropriate for hatcheries.     

Change in allometric length–weight relationship of Salmo trutta at emergence from the redd

In their life cycle, especially at early life stages, fishes pass through distinct growth stanzas with different length‐weight relationship patterns. Salmonid fish fry emergence from the redd gravel is a crucial moment in their life history. This study presents an ontogenic change in allometric length–weight relationship scaling of sea trout Salmo trutta at the time of emergence from the natural redds in a small lowland stream of western Lithuania. The paper also gives shrinkage rates and correction factors for emergent Salmo trutta fry after protracted formalin preservation.     

Fish condition in introduced tilapias of Ugandan crater lakes in relation to deforestation and fishing pressure

This study identifies environmental predictors of the condition of two introduced tilapia species (Oreochromis leucostictus and Tilapia zillii) that are known to have divergent trophic niches (planktivore and herbivore, respectively) in 17 crater lakes in western Uganda. We asked whether fish condition differs among lakes characterized by differences in fishing pressure and catchment deforestation; and we related relative condition factor to gradients of environmental variation across lakes. Lakes characterized by severe catchment deforestation tended to be lakes with high fishing pressure, so it was difficult to explore independent and interactive effects. However, mean relative condition factor was higher in populations with high fishing pressure compared to populations with low fishing pressure for both O. leucostictus and T. zillii. The condition of O. leucostictus populations was higher in lakes with severely deforested catchments; but mean relative condition factor of T. zillii did not differ between deforestation categories. Principal components analysis (PCA) was used to describe the major environmental gradients of variation among the lakes; and PCA factor scores were regressed against relative fish condition. The association between fish condition and environmental gradients was stronger for O. leucostictus than for T. zillii. For O. leucostictus, fish condition was related to PC1 (43% of the variance) and factors that loaded most heavily included Chl-a, water transparency, lake area and depth, suggesting higher condition in lakes characterized by higher primary productivity and smaller size. For T. zillii, PC3 (11%) was the only axis related to fish condition; and factors that loaded most heavily included lake area (positive), and conductivity and total nitrogen (negative). Some of the larger lakes are characterized by higher availability of macrophytes that may positively affect the food base for T. zillii.