Wild fish populations are currently experiencing unprecedented pressures, which are projected to intensify in the coming decades. Developing a thorough understanding of the influences of both biotic and abiotic factors on fish populations is a salient issue in contemporary fish conservation and management. During the 50th Anniversary Symposium of The Fisheries Society of the British Isles at the University of Exeter, UK, in July 2017, scientists from diverse research backgrounds gathered to discuss key topics under the broad umbrella of 'Understanding Fish Populations'. Below, the output of one such discussion group is detailed, focusing on tools used to investigate natural fish populations. Five main groups of approaches were identified: tagging and telemetry; molecular tools; survey tools; statistical and modelling tools; tissue analyses. The appraisal covered current challenges and potential solutions for each of these topics. In addition, three key themes were identified as applicable across all tool-based applications. These included data management, public engagement, and fisheries policy and governance. The continued innovation of tools and capacity to integrate interdisciplinary approaches into the future assessment and management of fish populations is highlighted as an important focus for the next 50 years of fisheries research.

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Sarcocystis spp. are cysts-forming coccidian parasites which infect several animals including camels as intermediate hosts. The present study was designed to study the Sarcocystis infection in camels (Camelus dromedaries) at morphological and molecular levels. Samples of the esophageal, heart and ocular muscle tissues were collected from infected camels in El-kharga, New Valley Governorate, Egypt. Samples were examined for Sarcocystis spp. infection using macroscopic evaluation, light microscopy (LM), transmission electron microscopy (TEM), and molecular analysis. LM examinations revealed 106 of 124 muscle samples (85.5%) were positive for Sarcocystis. Two species Sarcocystis cameli and Sarcocystis ippeni were recognized. In light microscopy, Sarcocystis were thin walled with barely visible projections. Using the TEM, the two structurally distinct Sarcocystis were recognized by unique villar protrusions (Vp). Sarcocystis of S. cameli had Vp of the type 9j. The Sarcocystis wall had upright slender Vp, up to 0.1-0.4 μm long and 0•05-0.1 μm wide. On each Vp, Rows of knob-like protrusions were observed to be interconnected. Sarcocystis ippeni had ''type 32'' Sarcocystis wall have been characterized by conical Vp with an electron dense knob. The Vp were approximately 175.27-266.76 nm long and 100.45-175.98 nm wide. In each Sarcocystis, the Vp had microtubules (Mt) that originated at midpoint of the ground substance (Gs) and continued up to the tip. Molecular data revealed the amplification of partial fragments of the 18S rRNA gene (~600 bp). The digestion analysis of obtained PCR products using Restriction fragment length polymorphism (RFLP) method utilizing (Mbo1) appeared 2 bands approximately 250 and 350 bp for each Sarcocystis. Molecular analysis demonstared the ability of 18S rRNA gene for distinguishing Sarcocystis species in studied animals and to be used as molecular marker.

INTRODUCTION Genetic variation (polymorphisms) caused by mutational alterations are necessitated for species survival and adaptations in diverse environmental conditions (Fisher, 1930).The patterns of genetic discrepancy to species level can be exposed using tools of molecular genetic markers (Linda and Paul, 1995). Such information of molecular markers-based on decipherable polymorphism at DNA and protein levels are source of knowledge for several research applications including molecular ARTICLE INFO

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