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Cm Fork Length (cm + fork_length)
Selected AbstractsVertical movements of bigeye tuna (Thunnus obesus) associated with islands, buoys, and seamounts near the main Hawaiian Islands from archival tagging dataFISHERIES OCEANOGRAPHY, Issue 3 2003Michael K. Musyl Abstract To learn more about the movement patterns of bigeye tuna (Thunnus obesus), we deployed archival tags on 87 fish ranging in fork length from 50 to 154 cm. Thirteen fish were recaptured, from which 11 archival tags were returned, representing in aggregate 943 days-at-liberty. We successfully retrieved data from 10 tags, representing 474 days in aggregate. The largest fish recaptured was 44.5 kg [131 cm fork length (FL)] and the smallest 2.8 kg (52 cm). The deepest descent recorded was 817 m, the coldest temperature visited 4.7°C, and minimum oxygen level reached ,1 mL L,1. Fish spent little time at depths where water temperatures were below 7°C and oxygen levels less than ,2 mL L,1. Five fish were recaptured near the offshore weather buoy where they were tagged. Based on vertical movement patterns, it appeared that all stayed immediately associated with the buoy for up to 34 days. During this time they remained primarily in the uniform temperature surface layer (i.e. above 100 m). In contrast, fish not associated with a floating object showed the W-shaped vertical movement patterns during the day characteristic of bigeye tuna (i.e. descending to ,300,500 m and then returning regularly to the surface layer). Four fish were tagged and subsequently recaptured near Cross Seamount up to 76 days later. These fish exhibited vertical movement patterns similar to, but less regular than, those of fish not associated with any structure. Bigeye tuna appear to follow the diel vertical movements of the deep sound scattering layer (SSL) organisms and thus to exploit them effectively as a prey resource. Average night-time depth was correlated with lunar illumination, a behaviour which mimics movements of the SSL. [source] Reproduction in Bagre marinus (Ariidae) off Pernambuco, northeastern BrazilJOURNAL OF APPLIED ICHTHYOLOGY, Issue 3 2006P. Pinheiro Summary Throughout 1997, the catches of artisanal gillnetters working off the coast of northeastern Brazil were sampled monthly for Bagre marinus (Mitchill 1815). Significantly more females (n = 207) than males (n = 82) were caught, although there was no significant difference in their size compositions (21,47 cm fork length, FL). All males sampled (21,40 cm FL) had developed gonads and were classified as sexually mature. According to macroscopic and microscopic examination of their reproductive tract, females were separated into four reproductive stages (immature, maturing, mature, and resting). Size at 50% sexual maturity for females was estimated to be 33 cm FL. A positive linear relationship was detected between the size of mature females and their fecundity (between 11 and 32 oocytes). Clear reproductive progress indicated a spawning period between March and May. We conclude that further fishery-independent data are required to determine patterns of male abundances and distributions. [source] Some aspects of the biology of the stargazer mountain catfish, Amphilius uranoscopus (pfeffer); (Siluriformes: Amphiliidae) indigenous to Kenya streamsAFRICAN JOURNAL OF ECOLOGY, Issue 4 2009Charles C. Ngugi Abstract A study on some biological parameters of the mountain catfish, Amphilius uranoscopus Pfeffer 1889 (Silurifomes: Amphiliidae), was carried out in the Thego stream on the slopes of Mount Kenya from February to December 2002. Physical and chemical profiles of the Thego show that the water quality parameters is typical of high altitude streams with temperatures rarely exceeding 18°C, DO ranging from 7.9 to 8.2 mg l,1 and relatively high conductivity (97,137 ,S cm,1) typical of perturbed lotic environments. A total of 1010 fish were caught by an electro-fisher, with sizes ranging between 8 and 24 cm fork length. The population structure had a unimodal distribution with maxima at 14,16 cm. The length,weight relationship showed relatively narrow range in the slope ranging from 2.61 in April to 2.98 in February 2002, thereby suggesting isometric growth pattern. The fitted growth pattern of A. uranoscopus showed an asymptotic length (L,) of 28.5 cm and a growth curvature (K) of 0.56 year,1 resulting in an estimated natural mortality coefficient (M) of 0.90 year,1. The Fulton's condition factor (K) was also relatively stable with a peak in April (0.92 ± 0.21) and lowest value in June (0.86 ± 0.10). As A. uranoscopus is not under commercial exploitation, the seemingly depressed population is possibly attributed to the introduced exotic rainbow trout that heavily predates on the species and environmental perturbations arising from changes in land use. The implications of such changes on A. uranoscopus are discussed. Résumé Une étude de certains paramètres du poisson-chat de montagne Amphilius uranoscopus Pfeffer 1889 (Silurifomes: Amphiliidae) a été réalisée dans le courant du Thego, sur les pentes du mont Kenya entre février et décembre 2002. Le profil physique et chimique du Thego montre que les paramètres de la qualité de l'eau sont typiques des cours d'eau de haute altitude, avec une température qui dépasse rarement 18°C, un OD qui varie de 7,9 à 8,2 mg/l, et une conductivité relativement haute (87 à 137 ,S/cm) typique d'environnements lotiques perturbés. Au total, 1 010 poissons ont été capturés au moyen d'une canne électrique, d'une taille allant de 8 à 24 cm de longueur à la fourche. La structure de la population avait une distribution unimodale avec des maxima de 14,16 cm. La relation longueur/poids présente une variation relativement étroite dans la pente, allant de 2,61 en avril à 2,98 en février 2002, ce qui suggère un schéma de croissance isométrique. Le schéma de croissance intégré d'A. uranoscopus montre une longueur asymptotique (L,) de 28,5 cm et une courbure de croissance (K) de 0,56/an, résultant en un coefficient de mortalité naturelle estimé (M) de 0,90/an. Le facteur de condition de Fulton (K) était aussi relativement stable, avec un pic en avril (0,92 ± 0,21) et la valeur la plus basse en juin (0,86 ± 0,10). Puisque A. uranoscopus ne fait pas l'objet d'une exploitation commerciale, la dépression apparente de la population doit peut-être être attribuée à la truite arc-en-ciel, espèce exotique introduite qui se nourrit abondamment de l'espèce, et à des perturbations environnementales provoquées par des changements d'utilisation des terres. Les implications de tels changements pour A. uranoscopus sont discutées. [source] Quantification of red myotomal muscle volume and geometry in the shortfin mako shark (Isurus oxyrinchus) and the salmon shark (Lamna ditropis) using T1 -weighted magnetic resonance imagingJOURNAL OF MORPHOLOGY, Issue 4 2007Cameron N. Perry Abstract T1 -weighted magnetic resonance imaging (MRI) in conjunction with image and segmentation analysis (i.e., the process of digitally partitioning tissues based on specified MR image characteristics) was evaluated as a noninvasive alternative for differentiating muscle fiber types and quantifying the amounts of slow, red aerobic muscle in the shortfin mako shark (Isurus oxyrinchus) and the salmon shark (Lamna ditropis). MRI-determinations of red muscle quantity and position made for the mid-body sections of three mako sharks (73.5,110 cm fork length, FL) are in close agreement (within the 95% confidence intervals) with data obtained for the same sections by the conventional dissection method involving serial cross-sectioning and volumetric analyses, and with previously reported findings for this species. The overall distribution of salmon shark red muscle as a function of body fork length was also found to be consistent with previously acquired serial dissection data for this species; however, MR imaging revealed an anterior shift in peak red muscle cross-sectional area corresponding to an increase in body mass. Moreover, MRI facilitated visualization of the intact and anatomically correct relationship of tendon linking the red muscle and the caudal peduncle. This study thus demonstrates that MRI is effective in acquiring high-resolution three-dimensional digital data with high contrast between different fish tissue types. Relative to serial dissection, MRI allows more precise quantification of the position, volume, and other details about the types of muscle within the fish myotome, while conserving specimen structural integrity. J. Morphol., 2007. © 2007 Wiley-Liss, Inc. [source] | |||||||||||||