Fish and macroinvertebrate assemblages reveal extensive degradation of the world's rivers.

Rivers suffer from multiple stressors acting simultaneously on their biota, but the consequences are poorly quantified at the global scale. We evaluated the biological condition of rivers globally, including the largest proportion of countries from the Global South published to date. We gathered macroinvertebrate- and fish-based assessments from 72,275 and 37,676 sites, respectively, from 64 study regions across six continents and 45 nations. Because assessments were based on differing methods, different systems were consolidated into a 3-class system: Good, Impaired, or Severely Impaired, following common guidelines. The proportion of sites in each class by study area was calculated and each region was assigned a Köppen-Geiger climate type, Human Footprint score (addressing landscape alterations), Human Development Index (HDI) score (addressing social welfare), % rivers with good ambient water quality, % protected freshwater key biodiversity areas; and % of forest area net change rate. We found that 50% of macroinvertebrate sites and 42% of fish sites were in Good condition, whereas 21% and 29% were Severely Impaired, respectively. The poorest biological conditions occurred in Arid and Equatorial climates and the best conditions occurred in Snow climates. Severely Impaired conditions were associated (Pearson correlation coefficient) with higher HDI scores, poorer physico-chemical water quality, and lower proportions of protected freshwater areas. Good biological conditions were associated with good water quality and increased forested areas. It is essential to implement statutory bioassessment programs in Asian, African, and South American countries, and continue them in Oceania, Europe, and North America. There is a need to invest in assessments based on fish, as there is less information globally and fish were strong indicators of degradation. Our study highlights a need to increase the extent and number of protected river catchments, preserve and restore natural forested areas in the catchments, treat wastewater discharges, and improve river connectivity.

Effect of anesthetic, tag size, and surgeon experience on postsurgical recovering after implantation of electronic tags in a neotropical fish: Prochilodus lineatus (Valenciennes, 1837) (Characiformes: Prochilodontidae)

Implantation of telemetry transmitters in fish can be affected by different parameters. This study aimed to evaluate the effect of type of anesthetic, tag size, and surgeon experience on surgical and postsurgical wound healing in the neotropical fish Prochilodus lineatus . In total, eighty fish were surgically implanted with telemetry transmitters and forty fish were kept as controls. Forty fish were implanted with a small tag and other forty were implanted with a large tag. Similarly, forty fish were anesthetized with eugenol and forty fish were anesthetized by electroanesthesia, and forty surgeries were performed by an expert surgeon and forty surgeries were performed by novice surgeons. At the end of the experimental period seventeen (21.3%) tagged fish had postsurgical complications, including death (1.3%), tag expulsion (2.5%), antenna migration (2.5%), and infection (15%). Tag size was the key determinant for postsurgical complications. Surgical details and postsurgical wound healing were not affected by type of anesthetic. Incision size, duration of surgery, and wound area were significantly affected by tag size and surgeon experience, and the number of sutures was significantly affected by tag size only. The results indicate that successful implantation of telemetry transmitters is dependent upon surgeon experience and tag size.(AU)

A implantação de transmissores em peixes pode ser afetada por diversos aspectos. Este estudo objetivou avaliar a influência do tamanho do transmissor, do tipo de anestésico e da experiência do cirurgião em parâmetros cirúrgicos e recuperação pós-cirúrgica do peixe neotropical Prochilodus lineatus . Foram marcados oitenta indivíduos com transmissores de telemetria, enquanto outros quarenta foram utilizados como controle. Quarenta indivíduos foram marcados com um transmissor pequeno e outros quarenta com um transmissor maior. Foram utilizados dois tipos de anestésico sendo quarenta indivíduos anestesiados por eletronarcose e outros 40 por eugenol e as cirurgias foram realizadas por dois grupos de cirurgiões, experientes e inexperientes com quarenta peixes em cada grupo. Dezessete peixes (21,3%) apresentaram impactos diretos resultantes da cirurgia como o óbito (1,3%), perda do transmissor (2,5%), migração da antena (2,5%) e infecções internas (15%). Estes efeitos estão ligados ao tamanho do transmissor utilizado. A experiência do cirurgião possui relação direta em três parâmetros cirúrgicos (tamanho da incisão, tempo de cirurgia e área de cicatrização). O tamanho dos transmissores utilizados possui relação com quatro parâmetros (tamanho da incisão cirúrgica, número de suturas utilizadas, tempo de cirurgia e área de cicatrização). O anestésico não teve relação com os parâmetros cirúrgicos. Os resultados indicam que tanto a dimensão dos transmissores quanto a experiência dos cirurgiões têm impacto direto no sucesso de implantação dos transmissores.(AU)