Length-weight relationship and morphometrics of Osmerus eperlanus populations from two lakes of northeastern Poland

This study provides the length-weight relationship (LWR) of European smelt (Osmerus eperlanus) occurring in two lakes in northeastern Poland. The morphometric characters of the two populations of this species in lakes Dargin and Dejguny were also compared. The LWRs were highly significant (P < 0.05) with a high coefficient of determination (r2 ≥ 0.923). The estimated b values ranged from 3.256 to 3.508. Sixteen of the 26 morphological characters measured differed between the two populations. No sexual dimorphism was observed. The research presents detailed data on the biometric characters of the species that contributes to the assessment of phenotypic plasticity and general morphological variation of the populations.

First record of six marine fish species caught occasionally in the northern Arabian Sea in Pakistan

The present article presents the results of a recent independent fishery survey conducted in the northern Arabian Sea off the coast of Pakistan in 2016–2018. The survey confirmed the underreported occurrence of six fish species that are now included in the ichthyofauna diversity of Pakistan: Ambassis natalensis, Pomadasys striatus, Narcine oculifera, Paramonacanthus choirocephalus, Paramonacanthus tricuspis, Chromis westaustralis. The fishes were collected with demersal trawls operated at the depth of 165 m (90 fathoms), and the taxonomy, habitat, and distribution range of each of the species were carefully examined and verified with information available in Eschmyer’s fish catalog, Fishbase, WoRMS, and FAO. It is necessary to update the marine ichthyofauna record of Pakistan with the detailed taxonomic descriptions of each species and their distribution ranges.

The current state of the turbot, Scophthalmus maximus (Linnaeus, 1758), population in the northwestern part of the Black Sea

Turbot is one of the most valuable fish species in the Black Sea commercial fishery. The serious, dramatic depletion of the turbot stock and catches that began in the 1980s was caused by overfishing and poor ecological conditions. The state of the turbot stock began to improve in the northwestern part of the Black Sea in 2016. Landings were at their 30-year maximum in this part of the sea. Catches per unit effort (CPUEs) have been at a stable, high level there for the last few years. Average turbot weight and length have also been increasing. The Stock Synthesis (SS3) framework was used in the stock assessment. According to SS3 analysis, fishing mortality (F) reached the minimum level of 0.29 in 2018. The cumulative SPR (Spawner Potential Rate) index was 0.27, which approximately equaled SPRMSY = 0.25. Thus, currently the turbot stock is mostly moderately exploited at a level close to the management target in the northwestern part of the Black Sea. However, the entire Black Sea population has not fully recovered yet.

Comparative study of length-weight relationships and biological indices of Himalayan snow trout, Schizothorax labiatus, inhabiting two lotic water bodies in the Kashmir Valley

The length-weight relationship (LWR) plays an important role in fishery management as it can be used to estimate the average weight of a specific length group. The results of the current study revealed that the mean values of regression coefficient b for both sexes of Schizothorax labiatus (McClelland) in the Jhelum River indicated positive allometric growth, while in the Sindh River, the b value for males indicated positive allometric growth and for females negative allometric growth. The value of coefficient of determination r2 for both sexes of S. labiatus was equal to or greater than 0.90 in both water bodies, except for females in the Sindh River. Higher significant (P < 0.05) average values of Fulton’s condition factor (K) and the hepatosomatic index (HSI) for both sexes of S. labiatus were noted in the Jhelum River than in the Sindh River. In contrast, higher significant (P < 0.05) values of the gonadosomatic index (GSI) were recorded in the Sindh River. The data generated during the current study provide basic information for researchers and fish biologists for the conservation and sustainable management of this commercially important food fish species in the Kashmir Valley.

Sublethal behavioral and biochemical toxicity of cypermethrin in juvenile Oreochromis niloticus in a static bioassay

Sublethal behavioral and biochemical toxicity of cypermethrin in Oreochromis niloticus (L.) juveniles was accessed under static conditions at concentrations of 0.5, 1.1, and 2.1 µg L−1 for up to eight weeks. The juveniles were highly sensitive to cypermethrin, with a 96-h LC50 of 12 µg L−1. Biphasic trends were noted for four avoidance behaviors: loss of equilibrium; erratic swimming; air gulping; opercular ventilation. Dose- and duration-dependent increases occurred in mucus secretion and color change. Mixed trends were noted for mean glutamate pyruvate transaminase, triglycerides, proteins, and cholesterol. These parameters decreased significantly depending on dose and duration in weeks two and six, but they increased in week eight. Mean glucose and glutamic oxaloacetic transaminase increased significantly depending on dose and duration up to week eight. No differences in glucose were noted in the control in week two. The findings of the present study confirmed that cypermethin adversely affected the health of fish even at a sublethal level.

Effects of functional feeds on hematological and biochemical indicators of juvenile sea trout (Salmo trutta m. trutta L.)

The effects functional additives had on blood hematological and biochemical indicators of sea trout (body weight 74.6 g, standard length 17.2 cm) were studied. The fish were divided into four experimental groups. Two groups were fed experimental feeds (group TU basic feed; group TUB basic feed with Bioimmuno), and two groups were fed commercial feeds (group TB commercial feed; group TBF commercial feed with FOCUS Plus®). After 14 and 28 days of rearing (the end of the experiment) specimens were measured and blood was drawn from seven fish from each group for hematological and biochemical tests. No effects were confirmed on rearing parameters. After 14 days of rearing, decreased values of WBC, RBC, HGB, and HCT were noted in groups TU and TB, while after 28 days lower values of RBC and HCT persisted in these groups. Lower values of these parameters were also noted in group TUB. Increased ALP activity was noted in group TUB after 14 days, while in groups TU and TUB increased levels of TP and ALB were noted after 28 days. A significant increase in ALB was also noted in group TBF. The functional feeds positively affected the physiological state of the sea trout. The results indicated that it is necessary to conduct studies to determine the optimal dose of Bioimmuno for juvenile sea trout and the period during which functional feeds should be given.

The perception of the issue of spawner harvesting in lakes by the owners and managers of the entities authorised to commercial and reacreational fisheries management

In recent years, the issue of spawner harvesting has been frequently addressed by different groups of stakeholders involved in the exploitation of fish resources. The increasingly numerous angling circles, which use these resources recreationally, question the current rules of fish stocking management in Poland, and its legal and economic status has become the focus of scientists’ interest. The aim of the study was to present and discuss the results of a questionnaire survey addressed to managers and owners of lake fisheries entities in order to identify the determinants of fisheries management related to spawner harvesting. Questionnaires were collected from a total of 76 entities, and concerned 1921 lakes with a total area of 174,078 ha, which accounts for more than 64% of the total area of lakes used for fishing and angling purposes in Poland. The paper presents inter alia the occupational characteristics of the respondents; their positions on the effect of spawner harvesting on lake ecosystem, environmental protection, and social factors; anglers’ assessments of spawner harvesting; the actual and potential methods for regulating this harvesting; and the negative and positive effects of the introduction of a prohibition on this harvesting. The results show that the respondents under study generally do not see the need for the introduction of additional (except those already in place) regulations concerning spawner harvesting, most of them notice the adverse effects of their introduction, but they are also aware of the possible changes and their impact on management.

Influence of effective microorganisms on pikeperch nonspecific humoral immunity, general condition, and development

Products containing effective microorganisms (EMTM) use microorganisms to work in the environment in which they are applied. EMTM is used in many countries worldwide, mainly in agriculture, including in aquaculture, and in environmental protection. Fish farmers use these products to stimulate effective growth and conditioning and as immunity enhancers. The aim of the study was to evaluate the effect of EMTM Probiotyk (Greenland, Poland) on the development of humoral non-specific resistance in pikeperch (Sander lucioperca) in the initial stage of rearing in recirculating aquaculture systems (RAS). The experimental diet was administered for 28 days with 0% (control group), 2%, and 4% EMTM supplementation. The results from the humoral parameters (Lys, TP, Ig) showed no statistical differences. The only statistically significant difference was noted in Cer for the 4% group. Non-specific humoral-mediated immunity in fish plays a key role in defense against damaging factors. Pikeperch is a fish used for restocking open waters, where fish can be subjected to agrotechnical treatments, including EMTM. The results permitted estimating the potential risks of using EMTM in aquaculture.

Some population characteristics of Oxynoemacheilus angorae (Steindachner, 1897) from the Perşembe Plateau meandering streams in Ordu, Turkey

The aim of the current study was to determine the length-weight relationship (LWR) and length-length relationship (LLR) with condition factor (K) values for Oxynoemacheilus angorae from the Perşembe Plateau meandering streams in Ordu, Turkey. A total of 65 fish specimens, which were caught with electrofishing gear, were examined. Fish standard length (SL), fork length (FL), total length (TL), and body weight (W) were determined. There were no statistical differences between the measurements of male and female O. angorae specimens; therefore, the female and male specimens were evaluated together in the current study. The LWR equation and determination coefficient of O. angorae were W = 0.014 TL2.7359 (r2 = 0.9659). The 95% confidence interval of the b value for the O. angorae specimens from the Perşembe Plateau meandering streams was 2.7261 to 2.7435. In the present study, it was determined that O. angorae specimens showed negative allometric growth. Calculations of O. angorae TL-SL, TL-FL, and FL-SL relationship equations and determination coefficients were as follows: TL = 0.2091+1.1646 SL, (r2 = 0.986); TL = 0.1341+1.0301 FL (r2 = 0.9914); and FL = 0.0998+1.1261 SL, (r2 = 0.9868), respectively. A new maximum total length was recorded for O. angorae in this study. The average condition factor value of O. angorae was 0.9954. This value could have indicated that this species was encountering some problems in this habitat. The O. angorae parameters determined were the first data reported for the Perşembe Plateau meandering streams in Ordu, Turkey (Middle Black Sea Region).

Influence of the size and form of Artemia sp. nauplii on the growth and survival of Atlantic sturgeon (Acipenser oxyrinchus Mitchill) larvae

The aim of the study was to determine the influence of the size and form of Artemia sp. feed on the rearing indices of Atlantic sturgeon larvae. In the experiment, the nauplius sizes used were 480 µm (group AD), 430 µm (group AM), and 430 µm frozen nauplii (group AI). After three weeks of rearing, the sturgeon from group AD had the highest mean body weight of 0.131 g that was statistically significantly different from groups AM (0.071 g) and AI (0.033 g). The longest total length was noted in group AD (2.8 cm) and was statistically different from the others (P ≤ 0.05). Specific growth rate in groups AD and AM was 14.7 and 11.8% d−1, respectively, and these values differed statistically from those in group AI at 7.8% d−1. The highest survival rate was recorded in group AD at 60.6%, while the lowest was noted in group AI at 15.6%, and the differences between these two groups were statistically significant. The results of the experiment indicated that a feed of live 480 µm Artemia sp. nauplius significantly accelerated the growth rates and increased the survival rates of Atlantic sturgeon larvae.