The various ways that anadromous salmonids use lake habitats to complete their life history

Despite the preponderance of exorheic lakes in rivers home to anadromous salmonids, little research has focused on how salmon, trout, and char use lakes as part of their anadromous life histories. The literature on this subject has so far revealed that some parr move into lakes to feed and grow before smoltification but that smolts moving through lakes tend to have high mortality in disproportion to what is observed in other habitats they migrate in or through. Adults have been observed using lakes for behavioural thermoregulation prior to spawning, and kelts of iteroparous species often exploit lakes to overwinter before returning to sea to recondition. We summarized knowledge on lakes as salmonid habitat and identified knowledge gaps about the use of lakes by anadromous salmonids related to whether lakes are barriers that structure genetics of populations, whether mortality in lakes is compensatory or additive, and whether systems with lakes have higher rates of repeat spawning among iteroparous salmonids. Human activities that alter lakes require further study to understand how changes in temperature, oxygen, ice, or circulation affect navigation and fate.

A LATE MIOCENE – EARLY PLIOCENE PARATETHYAN TYPE OSTRACOD FAUNA FROM THE DENIZLI BASIN (SW ANATOLIA) AND ITS PALAEOGEOGRAPHIC IMPLICATIONS

The upper Miocene – lower Pliocene sedimentary succession of the Denizli Basin (SW Anatolia) displays a unique record of undisturbed stratigraphy and provides an excellent opportunity to study long-term palaeoecological changes. This paper documents the ostracod assemblages of two sections of the Neogene Kolankaya Formation, resulting in the following taxonomic, palaeobiogeographic and ecological interpretations. The ostracod assemblages from the two sections consist of a mixture of oligohaline to mesohaline tolerant taxa but expose fundamental differences in their composition. This is reflected by the fact that out of 32 determined species, both sections only have 3 in common. In the stratigraphic older succession, the diverse ostracod fauna resembles taxa known from the Paratethys. Faunal relations to the brackish lake habitats of the Euxinic and Pannonian basins are apparent and the palaeobiogeographic significance of the fauna is discussed. The ostracod association of the younger section indicates a low brackish water habitat with fluctuating salinities, most likely in the oligohaline range. The ostracod assemblage of the Kolankaya Formation only permits a broad age assignment to the late Miocene – early Pliocene.

Food habits and trophic level of Anabas testudineus in floodplain lake, Lake Semayang, East Kalimantan

This research studied the food habits and trophic level of A. testudineus in a floodplain lake, Lake Semayang, East Kalimantan. The lake has characteristics of both swamp and lake habitats. The research was conducted from February 2017 until January 2018. During the study, 558 samples of Anabas testudineus were analyzed. The Index of Stomach Content (ISC) in the swamp habitats ranged from 4.32 - 39.59%, with an average of 19.35%, while in the lake habitat ranged from 3.68 - 38.46% with an average of 16.03%. Index of Preponderance (IP) value showed the dominant food item in the fish stomach is animal (62.58 - 79.66%), plants (25.18 - 42%), and undetectable food (≥ 5%). Based on the type and composition of the food, A. testudineus can be classified as omnivorous more inclined to carnivorous. The trophic level of this species changes along with increasing size length.

Reassessment of the threatened status of IUCN red listed Indian river shad Gudusia chapra (Hamilton, 1822) from Bangladesh

The Indian river shad, Gudusia chapra, locally known as chapila fish is rich in nutritive values and important to artisanal and subsistence fisheries in Bangladesh. The conservation status of this species is of particular interest due to its recent decline in rivers. To assess the current status of this species in Bangladesh, we recorded its abundance at seven sites in the Padma, the Meghna and the Tetulia rivers during pre-monsoon, monsoon and post-monsoon seasons. In this study, G. chapra was consistently recorded in the study area and there was no significant temporal or spatial variation in its abundance. The observed mean length and weight of the species were similar to those recorded in earlier studies. Currently, G. chapra is listed as vulnerable species in the IUCN Red List of Threatened Species in Bangladesh. Although the primary known habitat of this species is river, IUCN assessment was based on production from beel and Kaptai Lake habitats. In this study, consistent occurrence and availability of the species across spatial and temporal scales in rivers suggest the necessity to reassess the conservation status of G. chapra in the country. Dhaka Univ. J. Biol. Sci. 28(1): 83-91, 2019 (January)