Understanding the population structure of a species and the barriers that disrupt dispersal is important to accurately assess the global conservation status and manage the risk of local extinction. This is especially true for species of commercial importance (Begg et al., 1999) or conservation concern (Moritz, 1994), which are impacted disproportionally by anthropogenic or environmental pressures. Dispersal

The Critically Endangered largetooth sawfish Pristis pristis is one of the most threatened elasmobranch species and is currently thought to be locally extinct in at least 27 countries. Although largetooth sawfish information in Central America is scarce, recent records show that this species is still present in Costa Rica, yet its distribution and current status remain unclear. This study investigated the spatial and temporal distribution of the largetooth sawfish in Costa Rica and identified local threats affecting the populations. We conducted 275 structured interviews in coastal and riverine communities across the country, which resulted in 134 confirmed records in the Pacific, 1 in the Caribbean and 51 in the northern region. Historical and recent records suggest the largetooth sawfish has undergone significant reductions in abundance and distribution from coastal and riverine areas, mainly due to interaction with fishing gear such as gill nets and hook and line. Most sawfish captured by gill nets were reported in the Central Pacific region, whereas hook and line records were more common in the northern region and the South Pacific. Although largetooth sawfish populations in Costa Rica have followed the global decline trend, we found 2 main hotspots where recent sightings and captures appear to be more common, suggesting there is still hope for the species to recover in Costa Rica and possibly in the region. Moreover, Costa Rica recently became the 17 th country to ratify national legal protection for sawfishes, which may strengthen conservation efforts to protect populations locally and in the Central American region.

Ichthyofaunal diversity in Laguna Hule, Costa Rica. Laguna Hule is a volcanic origin crater which has been flooded over time, resulting in a deep mass of water with no previous studies about its fish community. For five months we sampled it and a draining stream (Pata de Gallo) with nets, and hook and line. The captured specimens were identified in situ to the possible lowest taxonomic level. The lagoon mostly had species normally found near aquatic vegetation: Amatitlania siquia, Amphilophus alfari, Astyanax aeneus, Cynodonichthys sp., Parachromis dovii, Phallichthys amates and Poecilia gillii (dominant: A. aeneus, P. gillii and P. amates). The stream was dominated by Brachyrhaphis olomina but also had Rhamdia laticauda. The low diversity indices (1,48 in the lagoon and 0,26 in the stream) are characteristic of lacustrine ecosystems. Females were, as expected, larger and more abundant in P. amates and B. olomina; whereas in P. gilli, some males were larger. The area is affected by pollution, introduction of invasive species, uncontrolled fishing and use of destructive fishing gear. We propose demarcation of site protection status and organizing a community group to protect this fish community.Key words: Hule lagoon, ichthyology, fish diversity, fresh water fish RESUMEN: La laguna Hule es un cráter de origen volcánico que se ha inundado con el tiempo, dando como resultado una gran masa de agua, sin estudios previos sobre su comunidad de peces. Muestreamos durante cinco meses la laguna y una quebrada (Pata de Gallo) con redes, gancho y línea. Los especímenes capturados se identificaron in situ al nivel taxonómico posible más bajo. La laguna tenía especies que normalmente se encuentran cerca de la vegetación acuática: Amatitlania siquia, Amphilophus alfari, Astyanax aeneus, Cynodonichthys sp., Parachromis dovii, Phallichthys amates y Poecilia gillii (dominante: A. aeneus, P. gillii y P. amates). La quebrada estaba dominada por Brachyrhaphis olomina pero también tenía Rhamdia laticauda. Los índi-ces de baja diversidad (1,48 en la laguna y 0,26 en la quebrada) son característicos de los ecosistemas lacustres. Las hembras fueron, como se esperaba, más grandes y abundantes en P. amates y B. olomina; mientras que en P. gilli, algunos machos eran más grandes. El área se ve afectada por la contaminación, la introducción de especies invasoras, la pesca incontrolada y el uso de equipo destructivo de pesca. Proponemos la demarcación del estado de protección del sitio y la organización de un grupo comunitario para proteger a esta comunidad de peces.

Understanding the population structure of a species is important to accurately assess its conservation status and manage the risk of local extinction. The Bull Shark (Carcharhinus leucas) faces varying levels of exploitation around the world due to its coastal distribution. Information regarding population connectivity is crucial to evaluate its conservation status and local fishing impacts. In this study, we sampled 922 putative Bull Sharks from 19 locations in the first global assessment of population structure of this cosmopolitan species. Using a recently developed DNA-capture approach (DArTcap), samples were genotyped for 3,400 nuclear markers. Additionally, full mitochondrial genomes of 384 Indo-Pacific samples were sequenced. Reproductive isolation was found between and across ocean basins (eastern Pacific, western Atlantic, eastern Atlantic, Indo-West Pacific) with distinct island populations in Japan and Fiji. Bull Sharks appear to maintain reproductive connectivity using shallow coastal waters as dispersal corridors, whereas large oceanic distances and historical land-bridges act as barriers. Females tend to return to the same area for reproduction, making them more susceptible to local threats and an important focus for management actions. Given these behaviours, the exploitation of Bull Sharks from insular populations, such as Japan and Fiji, may instigate local decline that cannot readily be replenished by immigration, which can in turn affect ecosystem dynamics and functions. These data also supported the development of a genetic panel to ascertain the population of origin, which will be useful in monitoring the trade of fisheries products and assessing population-level impacts of this harvest.