Traps and netting, better together than alone: an innovative approach to improve Procambarus clarkii management

The red swamp crayfish Procambarus clarkii is the most widespread invasive crayfish in Europe, and responsible for a plethora of negative impacts on aquatic ecosystems. Most capture methods used for controlling crayfish populations have a bias towards the capture of adults, however, the removal of the young-of-the-year crayfish (YOY) may be essential for achieving effective control of invasive populations. This paper analysed the crayfish caught during a management campaign carried out in five permanent stream pools from southern Spain. We compared size structure, CPUE and sex-ratio obtained with two control methods: cylindrical traps (a method commonly used in crayfish management) and horizontal hauls using a fine-mesh net (inspired by zooplankton sampling techniques). Horizontal hauls showed a higher selectivity for catching YOY and higher efficiency (eight-fold) than traps. The combined use of both gears increased total catch by 46%. Our results suggest that YOY may be sharply underestimated if only cylindrical traps are used. The YOY cohort represented 60% of the total catch during the management campaign. Therefore, active netting with a fine mesh may be a complementary method to the use of traps in order to manage invasive populations of P. clarkii and may provide a better understanding of the structure and dynamics of invasive crayfish populations.

Inside Doctor Livingstone: a Scottish icon's encounter with tropical disease

SUMMARYDr David Livingstone died on May 1st 1873. He was 60 years old and had spent much of the previous 30 years walking across large stretches of Southern Africa, exploring the terrain he hoped could provide new environments in which Europeans and Africans could cohabit on equal terms and bring prosperity to a part of the world he saw ravaged by the slave trade. Just days before he died, he wrote in his journal about the permanent stream of blood that he was emitting related to haemorrhoids and the acute intestinal pain that had left him incapable of walking. What actually killed Livingstone is unknown, yet the years spent exploring sub-Saharan Africa undoubtedly exposed him to a gamut of parasitic and other infectious diseases. Some of these we can be certain of. He wrote prolifically and described his encounters with malaria, relapsing fevers, parasitic helminths and more. His graphic writing allows us to explore his own encounters with tropical diseases and how European visitors to Africa considered them at this time. This paper outlines Livingstone's life and his contributions to understanding parasitic diseases.

Correlation of Red-Shouldered Hawk Abundance and Macrohabitat Characteristics in Southern Ohio

We measured an index of Red-shouldered Hawk (Buteo lineatus) abundance along streams in southern Ohio and related differences in abundance index to landscape-scale habitat characteristics within the surveyed areas. Fifteen study sites, each a 5.8-km reach of a permanent stream, were surveyed four times using broadcasts of Red-shouldered Hawk calls and Red-tailed Hawk (Buteo jamaicensis) calls. We determined the landcover types in a corridor surrounding each surveyed area using a GIS landcover data grid, and counted the number of small ponds within each corridor. We calculated hawk response rate for each species as the mean number of visual or aural detections per survey. Red-shouldered Hawk response rate was inversely correlated to Red-tailed Hawk response rate (r = −0.52, P < 0.04), and was positively correlated to the number of small ponds within each stream corridor (r = 0.77, P < 0.01), suggesting that the number of small ponds was an important factor associated with Red-shouldered Hawk abundance. Correlación entre la Abundancia de Buteo lineatus y Características de Macrohábitat en el Sur de Ohio Resumen. Calculamos un índice de abundancia de Buteo lineatus a lo largo de varios arroyos en el sur de Ohio y relacionamos las diferencias en este índice con características del hábitat a escala del paisaje de las áreas censadas. Trabajamos en 15 sitios (cada uno comprendiendo 5.8 km alrededor de un arroyo permanente), que fueron censados cuatro veces reproduciendo vocalizaciones de B. lineatus y B. jamaicensis. Determinamos el tipo de uso de la tierra en un corredor alrededor de cada área censada utilizando un sistema de información geográfica y contamos el número de pequeños estanques al interior de cada corredor. Calculamos la tasa de respuesta de las dos especies de gavilanes como el número promedio de detecciones visuales o auditivas por censo. La tasa de respuesta de B. lineatus se correlacionó negativamente con la tasa de respuesta de B. jamaicensis (r = −0.52, P < 0.04) y positivamente con el número de estanques dentro de cada corredor (r = 0.77, P < 0.01). Los resultados sugieren que el número de estanques es un factor importante asociado a la abundancia de B. lineatus.

Rheotactic Differentiation between Fluvial and Lacustrine Populations of Arctic Grayling (Thymallus arcticus), and Implications for the Only Remaining Indigenous Population of Fluvial "Montana Grayling"

Rheotactic behavior of young Arctic grayling (Thymallus arcticus) from fluvial (Big Hole River) and lacustrine (Red Rocks Lake) populations in Montana was assessed in an artificial stream to see if fluvial grayling are adapted to life-long residence in streams by having an innately greater tendency to hold position and lesser tendency to go downstream. Responses of young tested at 0–10 d post-swimup contradicted the hypothesis; the fluvial grayling had strong downstream responses similar to or greater than those of the lacustrine grayling. When tested 18–31 d post-swimup, however, rheotactic responses of the fluvial and lacustrine grayling were consistent with the hypothesis, at three light intensities (full and dim lighting and darkness). Rheotactic differences were even greater in trials at 47–72 d post-swimup (conducted only under full lighting). Big Hole River grayling appear to be adapted to permanent stream residence. Such adaptation reinforces the importance of conserving this last indigenous fluvial population of the geographically disjunct, genetically identifiable "Montana grayling."

A preliminary report on the stone artefacts from Colless Creek Cave, northwest Queensland

Today the gorge system of which Colless Creek is a part is an oasis, a permanent stream system lined by tropical gallery forest running through semi-arid terrain. Colless Creek Cave itself is currently an oasis of information within the archaeological literary desert of the Top End; no other sites have been published within a 500km radius. This paper is a preliminary report on the analysis of stone artefacts from the cave. It is preliminary in two senses. First, it analyses material from only two test squares excavated in 1979. Second, it describes only artefact densities, rates of discard, artefact sizes, and the proportions of artefact types. No analysis of stone working technology is presented. This paper is concerned only with chronological changes within the cave; no account is taken of spatial variations within the cave, or of relationships to other sites.