Size, connectivity and edge effects of stream habitats explain spatio-temporal variation in brown trout ( Salmo trutta ) density

Ecological theory postulates that the size and isolation of habitat patches impact the colonization/extinction dynamics that determine community species richness and population persistence. Given the key role of lotic habitats for life-history completion in rheophilic fish, evaluating how the distribution of swift-flowing habitats affects the abundance and dynamics of subpopulations is essential. Using extensive electrofishing data, we show that merging island biogeography with meta-population theory, where lotic habitats are considered as islands in a lentic matrix, can explain spatio-temporal variation in occurrence and density of brown trout ( Salmo trutta ). Subpopulations in larger and less isolated lotic habitat patches had higher average densities and smaller between-year density fluctuations. Larger lotic habitat patches also had a lower predicted risk of excessive zero-catches, indicative of lower extinction risk. Trout density further increased with distance from the edge of adjacent lentic habitats with predator ( Esox lucius ) presence, suggesting that edge- and matrix-related mortality contributes to the observed patterns. These results can inform the prioritization of sites for habitat restoration, dam removal and reintroduction by highlighting the role of suitable habitat size and connectivity in population abundance and stability for riverine fish populations.

Response of fish assemblage structure to changing flood and flow pulses in a large subtropical river

Fish assemblages recorded from August 2010 to July 2013 in two lotic and lentic environments of the Middle Paraná River floodplain were studied in the light of flood and flow pulse variations. Three flood pulses occurred during the period of study, each with a different magnitude, duration and timing. Instead four flow pulses were recorded during this period. The varied hydrological conditions had an influence on the ichthyofauna. The fish species richness in both lentic and lotic habitat was negatively correlated with the maximum water level and fish assemblages were spatially and temporally structured according to their different reproductive strategies. Long- and short-distance migratory species were dominant after the flood pulse of the highest intensity and longest duration, whereas sedentary fish and internal fertilisation prevailed during flow pulses and lower flood pulses. Fish assemblage similarity was generally low between habitats during flood and flow pulses, but increased after those events depending on their magnitude, duration and timing. Apparently, flow pulses would also function like floods, as mechanisms of spatio-temporal structuring of fish assemblages.

Kelimpahan Serangga Air di Sungai Toraut Sulawesi Utara

Serangga air merupakan kelompok Arthropoda yang dapat dijumpai hampir pada jenis perairan misalnya pada habitat lentik atau lotik. Seranggan air dalam suatu ekosistem berperan penting dalam rantai makanan selain itu juga serangga air dapat dijadikan sebagai bioindikator terhadap penentuan kualitas suatu perairan. Penelitian ini bertujuan untuk menganalisis kelimpahan serangga air yang terdapat di Sungai Toraut. Lokai penelitian terletak pada Sub DAS dari DAS Dumoga Kabupaten Bolaang Mongondow, Sulawesi Utara. Sungai ini memiliki luas sekitar 249 km2 dan hulunya terletak di Taman Nasional Bogani Nani Wartabone (TNBNW). Penelitian ini menggunakan metode Purposive Random Sampling dengan menggunakan alat surber sampler. Total individu yang didapatkan dari 3 stasiun sebanyak 1497 individu dengan jumlah famili sebanyak 24 yang terdiri dari 27 spesies. Spesies serangga air yang paling banyak ditemukan pada stasiun satu, sedangkan yang sedikit pada stasiun 3. Kelimpahan spesies yang paling banyak ditemukan adalah Hydropsyche sp.Arthropods is a group of aquatic insects that can be found in almost all types of aquatic habitats for example lentic or lotic habitat. In the field of ecology, aquatic insects plays a role in the food chain, moreover the aquatic insects can be used as bioindicator to determine the quality of water. This study aims to analyze the abundance of aquatic insects found in the Toraut River. This study lies in the sub-watershed from the watershed of Dumoga Bolaang Mongondow, North Sulawesi. This river has an area of ​​approximately 249 km2 and its located in the headwaters of Bogani Nani Wartabone National Park. The method used in this study is purposive random sampling method by using a sampler surber. Total individuals were obtained from 3 stations are 1497 individuals with total 24 families consisting of 27 species. The most commonly species of aquatic insects found at station 1, whereas slightly at station 3. The most commonly species of aquatic insects found is Hydropsyche sp.

Why are the prevalence and diversity of helminths in the endemic Pyrenean brook newt Calotriton asper (Amphibia, Salamandridae) so low?

A cornerstone in parasitology is why some species or populations are more parasitized than others. Here we examine the influence of host characteristics and habitat on parasite prevalence. We studied the helminths parasitizing the Pyrenean brook newt Calotriton asper (n= 167), paying special attention to the relationship between parasites and ecological factors such as habitat, sex, ontogeny, body size and age of the host. We detected two species of parasites, Megalobatrachonema terdentatum (Nematoda: Kathlaniidae) and Brachycoelium salamandrae (Trematoda: Brachycoeliidae), with a prevalence of 5.99% and 1.2%, respectively. Marginally significant differences were found in the prevalence between sexes, with females being more parasitized than males. The present results show significant differences in the body length of paedomorphic and metamorphic individuals, the former being smaller. Nevertheless, no significant correlations between parasite prevalence and either newt body length, ontogenetic stage or age were found. In comparison with other Salamandridae living in ponds, prevalence and diversity values were low. This may be due to a long hibernation period, the species' lotic habitat and its reophilous lifestyle, which probably do not allow for a high parasite load.

The effect of flow regime on the occurrence of interference and exploitative competition in a salmonid species, white-spotted char (Salvelinus leucomaenis)

We examined the effect of flow regime on the occurrence of interference and exploitative competition in a salmonid species, white-spotted char ( Salvelinus leucomaenis ). In the lotic treatment, char showed typical consequences of interference competition (i.e., fish aggressively defended their foraging positions, and individuals occupying the most profitable positions grew fastest). In the lentic treatment, however, char behavior was consistent with exploitative competition; fish cruised over a larger area in search of food resources and showed limited aggression and no evidence of a dominance hierarchy. Our results indicate that white-spotted char showed interference competition more commonly than exploitative competition in the lotic habitat and vice versa in the lentic habitat.