Light Reflectance Characteristics and Remote Sensing of Waterlettuce

Waterlettuce ( Pistia stratiotes L.) is a free-floating exotic aquatic weed that often invades and clogs waterways in the southeastern United States. A study was conducted to evaluate the potential of using remote sensing technology to distinguish infestations of waterlettuce in Texas waterways. Field reflectance measurements showed that waterlettuce had higher visible green reflectance than associated plant species. Waterlettuce could be detected in both aerial color- infrared (CIR) photography and videography where it had light pink to pinkish-white image tonal responses. Computer analysis of CIR photographic and videographic images had overall accuracy assessments of 86% and 84%, respectively. (PDF contains 6 pages.)

Analysis of growth layers in the teeth of Tursiops truncatus using light microscopy, microradiography, and SEM

Preliminary results show microradiography and scanning electron microscopy (SEM) to be more accurate methods of accessing growth layer groups (GLGs) in the teeth of Tursiops truncatus than transmitted light microscopy. Microradiography shows the rhythmic deposition of mineral as alternating radiopaque and radiolucent layers. It improves the resolution of GLGs near the pulp cavity in older individuals, better than either SEM or light microscopy. SEM of etched sections show GLGs as ridges and grooves which are easily counted from the micrograph. SEM also shows GLGs to be composed of fine incremental layers of uniform size and number which may allow for more precise age determination. Accessory layers are usually hypomineralized layers within the hypermineralized layer of the GLG and are more readily distinguishable as such in SEM of etched sections and microradiographs than in thin sections viewed under transmitted light. The neonatal line is hypomineralized, appearing translucent under transmitted light, radiolucent in a microradiograph, and as a ridge in SEM. (PDF contains 6 pages.)

Behavioral and Physiological Responses to Light by the Sea Anemone Anthopleura elegantissima as Related to its Algal Endosymbionts

The endosymbiosis of algae with invertebrates may be viewed with at least two major orientations. On the one hand, one may focus on the plant and animal as essentially separate organisms living together, as the word symbiosis states. The products which are exchanged between the plant and animal and the effects of the association on either partner are then of particular interest. On the other hand, one may consider the partnership as an entity, and attempt to investigate the physiology, behavior, etc. of the symbiotic association, observing what differences may appear between the "plant-animal" and analogous non-symbiotic organisms. It is the second approach which I have tried to take in this thesis. I have concentrated on some effects of light on symbiotic and aposymbiotic sea anemones of the species Anthopleura elegantissima, particularly with respect to pigmentation and several types of behavior.

The distribution, abundance, and ecology of larval tunas from the entrance to the Gulf of California

ENGLISH: This study is based on collections of larvae of Thunnus albacares, Euthynnus llneatus, and Auxis sp. obtained from surface and oblique net tows made during seven cruises, each along a comparable track in the entrance of the Gulf of California and each during a different month. Concomitant measurements of surface temperature, salinity, and zooplankton were made at each of the plankton stations. The catches of larval Auxis sp. were examined by analysis of variance techniques to determine which environmental features were associated with the spawning of this tuna as indicated by the distribution of larvae and to gain some insight into the behavior of the larvae themselves. The testing indicated that the spawning of Auxis sp. varied significantly among the different months of the cruises. The testing also indicated that if the larvae were capable of avoiding the sampling apparatus, this ability was not related to features associated with time of day such as light conditions. The analysis did not detect any change in the vertical distribution of the larvae among the months of the experiment. It was concluded that the larvae did not exhibit a diel vertical movement. The measurements of temperature, salinity, and zooplankton volumes were treated as covariates in the analysis. The surface temperature proved to be a highly important factor in explaining the distribution of larvae, but salinity and zooplankton volumes were not. Catches of Thunnus albaeares and Euthynnus lineatus were rare during the course of the study; these are discussed in qualitative terms with respect to the time of the year and the surface temperature. The distribution of larval tunas in the area of study was compared with the distribution of surface water masses. It appeared that these masses had no influence per se on the distribution of larvae. SPANISH: Este estudio está basado en las recolecciones de larvas de Thunnus albacares, Eutbynnus lineatus, y Auxis sp. obtenidas según los arrastres superficiales y oblicuos de la red, realizados durante siete cruceros, cada uno a la entrada del Golfo de California a lo largo de un derrotero comparable, y cada uno durante distintos meses. Las mediciones correspondientes de la temperatura superficial, salinidad y de zooplancton se realizaron en cada una de las estaciones de plancton. Las capturas de larvas Auxís sp. fueron examinadas mediante el análisis de la varianza para determinar cuales características ambientales se encontraban asociadas con el desove de este atún según lo indicaba la distribución de las larvas, y para obtener alguna idea del comportamiento de las larvas en sí mismas. Las pruebas indicaron que el desove de Auxis sp. varió significativamente entre los diferentes meses de los cruceros; indicaron también que si las larvas eran capaces de evitar el aparato de muestreo, esta habilidad no se relacionaba a las características asociadas con la hora del día de acuerdo a las condiciones de luz. El análisis no demostró ningún cambio en la distribución vertical de las larvas durante los meses del experimento. Se determinó que las larvas no exhiben un movimiento vertical diario. Las mediciones de temperatura, salinidad, y de los volúmenes de zooplancton fueron tratadas como covariables en el análisis. La temperatura superficial demostró ser un factor altamente importante en la explicación de la distribución de las larvas, pero la salinidad y los volúmenes de zooplancton no lo fueron. Las capturas de Thunnus albacares y Eutbynnus lineatus fueron pocas durante el curso de este estudio; éstas se discuten en términos cualitativos respecto a la época del año y a la temperatura superficial. La distribución de los atunes larvales en el área de estudio fue comparada con la distribución de las masas superficiales de agua. Parece que estas masas no tienen influencia per se en la distribución de las larvas. (PDF contains 40 pages.)

Potentials for fisheries in the Niger Delta: Another green light for self sufficiency in regional food production

A discussion is presented on the potential for fishery development in the Niger Delta region, considering engineering activities and food production potentials of the freshwater zone and immediate hinterland, the brackishwater mangrove swamps and the estuaries. An examination of current trends in the environment indicates that a possible solution to improved exploitation of the region lies in hydraulic engineering, the manipulation of environmental conditions through varying freshwater and seawater inputs so as to increase aquatic and wetland productivity

Preliminary studies on the effects of light duration on the growth and performance of Clarias gariepinus fingerlings

The effects of light duration on the growth and performance of Clarias gariepinus fingerlings were investigated using artificial methods to simulate continuous day length and absolute darkness. The normal day length (12-H Light and 12-H Darkness) served as the control. Among some of the factors affected by the varying photoperiods there were body coloration, feeding efficiency, survival rate and Specific Growth Rate (SGR). There was notably no significant difference between the SGR of the 0-photoperiod culture and the control (P>0.05) but there was significant difference between the 0-photoperiod and the 24-H photoperiod experiment (P<0.05). The haematological profile analysed showed various degrees of changes in the blood parameters of fish cultured under different photoperiods. These changes however, did not show significant differences when subjected to statistical analysis

Reaction of fish to light (”Conclusions” only). [Translation from: Voprosy Ikhtiologii 6 17-20, 1956]

Qualitative and quantitative characteristics of the reaction of certain fish to light were tested and reasons for the attraction of certain fish to light are discussed.

Aspects of mineral composition of male and female Heterobranchus bidorsalis adults exposed to different concentrations of Bonny-light crude oil

Studies were carried out to assess some macro and trace elements of mineral composition of the male and female Heterobranchus bidorsalis adults exposed to graded concentrations (1.00-8.00m/L-1) of Bonny-light crude oil (BLCO). The experiment was monitored for 4 days (toxicity) and 42days (recovery) periods. Significant decreases (P < 0.05)in the sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), phosphorus (P), zinc (Zn), iron (Fe), vanadium (Va), lead (Pb) and manganese (Mn) contents of the male H. bidorsalis corresponded with the increasing concentrations of BLCO. In contrast, the female fishes recorded significant increases (P < 0.05) in the values of the above elements in their tissues as the concentrations of BLCO increased. Furthermore, the values of Na, K, Mg, Ca, P, Zn, Fe, Va, Pb and Mn recorded in the male fishes where generally lower than those of their female counterparts and the control fish. Increased values of these elements were also recorded during the recovery periods (days 14, 28 and 42) of this study in the magnitudes of 15% at day 14, 20% at day 28 and 20% at day 42. This implied that the removal of crude oil stress during this period improved the quantity of these minerals deposited in the fish tissues. The highest percent proportion of Zn and the lowest proportion of Pb recorded in both male and female H. bidorsalis adults agreed with the report of other workers for other fish species. KEYWORDS: Heterobranchus bidorsalis, Mineral composition, Bonny-light crude oil, Toxicity, Recovery.

Effects of rapid decompression and exposure to bright light on visual function in black rockfish (Sebastes melanops) and Pacific halibut (Hippoglossus stenolepis)

Demersal fishes hauled up from depth experience rapid decompression. In physoclists, this can cause overexpansion of the swim bladder and resultant injuries to multiple organs (barotrauma), including severe exophthalmia (“pop-eye”). Before release, fishes can also be subjected to asphyxia and exposure to direct sunlight. Little is known, however, about possible sensory deficits resulting from the events accompanying capture. To address this issue, electroretinography was used to measure the changes in retinal light sensitivity, flicker fusion frequency, and spectral sensitivity in black rockfish (Sebastes melanops) subjected to rapid decompression (from 4 atmospheres absolute [ATA] to 1 ATA) and Pacific halibut (Hippoglossus stenolepis) exposed to 15 minutes of simulated sunlight. Rapid decompression had no measurable influence on retinal function in black rockfish. In contrast, exposure to bright light significantly reduced retinal light sensitivity of Pacific halibut, predominately by affecting the photopigment which absorbs the green wavelengths of light (≈520–580 nm) most strongly. This detriment is likely to have severe consequences for postrelease foraging success in green-wavelength-dominated coastal waters. The visual system of Pacific halibut has characteristics typical of species adapted to low light environments, and these characteristics may underlie their vulnerability to injury from exposure to bright light.

Low cost light traps for coral reef fishery research and sustainable ornamental fisheries

Two relatively inexpensive light traps to capture pre-settling reef fish and invertebrates are described. A trap made from a plastic bucket (with plastic bottles, a small plastic waste bin and two sheets of plywood) that costs US$15 appears to be just as effective as a large aluminium and plexiglass trap that costs US$275.

Effects of current speed and turbidity on stationary light-trap catches of larval and juvenile fishes

Light traps are one of a number of different gears used to sample pelagic larval and juvenile fishes. In contrast to conventional towed nets, light traps primarily collect larger size classes, including settlement-size larvae (Choat et al., 1993; Hickford and Schiel, 1999 ; Hernandez and Shaw, 2003), and, therefore, have become important tools for discerning recruitment dynamics (Sponaugle and Cowen, 1996; Wilson, 2001). The relative ease with which multiple synoptic light trap samples can be taken means that larval distribution patterns can be mapped with greater spatial resolution (Doherty, 1987). Light traps are also useful for sampling shallow or structurally complex habitats where towed nets are ineffective or prohibited (Gregory and Powles, 1985; Brogan, 1994; Hernandez and Shaw, 2003).