Bass Fish

Individual striped bass Morone saxatilis were each exposed in random order to aquatic hypoxia (10% air saturation) either while swimming at 50% of their estimated critical swimming speed (Ucrit ) or while at rest until they lost equilibrium. Individuals were always less tolerant of hypoxia when swimming (P < 0.01); the average fish was over five times more tolerant to the same hypoxia exposure when not swimming. There was no relationship between an individual's rank order of hypoxia tolerance (HT) under the two flow regimes, suggesting that different factors determine an individual's HT when at rest than when swimming.

The structure of light- and dark-adapted retina of the black bass, Micropterus salmoides has been studied by light and electron microscopy. This retina lacks blood vessels at all levels. The optic fiber layer is divided into fascicles by the processes of Müller cells and the ganglion cell layer is represented by a single row of voluminous cells. The inner nuclear layer consists of two layers of horizontal cells and bipolar, amacrine and interplexiform cells. In the outer plexiform layer we observed the synaptic terminals of photoreceptor cells, rod spherules and cone pedicles and terminal processes of bipolar and horizontal cells. The spherules have a single synaptic ribbon and the pedicles possess multiple synaptic ribbons. Morphologically, we have identified three types of photoreceptors: rods, single cones and equal double cones which undergo retinomotor movements in response to changes in light conditions. The cones are arranged in a square mosaic whereas the rods are dispersed ...

Genetic diversity and divergence patterns of smallmouth bass Micropterus dolomieu spawning groups are analysed across its northern native range with mtDNA cytochrome b gene sequences and eight unlinked nuclear DNA microsatellite loci. Results reveal high levels of genetic variability and significant differences in allelic representation among populations (mtDNA: mean ± s.e., HD = 0·50 ± 0·06, mean ± s.e., θST = 0·41 ± 0·02 and microsatellites: mean ± s.e. HO = 0·46 ± 0·03, mean ± s.e. θST = 0·25 ± 0·01). The distributions of 28 variant mtDNA haplotypes, which differ by an average of 3·94 nucleotides (range = 1-8), denote divergent representation among geographic areas. Microsatellite data support nine primary population groups, whose high self-assignment probabilities likewise display marked divergence. Genetic patterns demonstrate: (1) high genetic diversity in both genomes, (2) significant divergence among populations, probably resulting from natal site homing and low lifetime migration, (3) support for three post-glacial refugia that variously contributed to the current northern populations, which remain evident today despite waterway connectivity and (4) a weak yet significant genetic isolation by geographic distance pattern, indicating that other processes affect the differences among populations, such as territoriality and site fidelity.

Biological invasions via anthropogenic vectors, intentional or not, are one of the main causes of ecological change in aquatic ecosystems. Micropterus salmoides (Lacepède, 1802) is often introduced for sport fishing purposes and is broadly distributed worldwide; it has been listed by IUCN as one of the 100 of the world’s worst invasive alien species. We conducted a systematic review of the literature using the ISI Web of Science and Scopus databases to synthesize the existing knowledge concerning introductions of M. salmoides introductions and their ecological impacts. We highlight major trends and gaps related to spatiotemporal patterns of the publications, research methods and ecological impacts. The number of publications relating to impacts of M. salmoides began to grow in the 1990’s and has been increasing in the last years. Studies of the species’ impact have been conducted in 16 countries, primarily in the Palearctic realm. There is a lack of studies in tropical and megadiverse regions. Most of the studies used field observational methodologies, with only a few theoretical studies. Most of the field observational studies were conducted in rivers and reservoirs. Impacts at the population and community levels, such as the local extirpation of native species and food web changes, were described more often than impacts at other biological levels. Finally we emphasize the necessity of developing management strategies in order to remove or, at least, control M. salmoides outside of its natural range and to deter additional introduction events into new habitats.