bluuebunny/crossref_metadata_2025 huggingface dataset:
Water quality and phytoplankton dynamics in Moreton Bay, south-eastern Queensland. II. Mathematical modelling.
Authors: McEwan James , Gabric Albert J. , Bell Peter R. F.
Published: August 2004

A coupled hydrodynamic water-quality model of Moreton Bay was developed to
enable better management of nutrient loads and to predict
eutrophication-related problems. The hydrodynamic submodel was calibrated to
available tidal data, and the transport submodel was calibrated to a salinity
dataset. A 15-month time-series of field data was used together with
historical data to calibrate and validate the water-quality submodel. Model
simulations suggest that denitrification removes over half the external N
inputs with about one-third exported to the open ocean. Approximately
8% of N and 20% of the P loading accumulates in the sediments.
Short-term variations due to hydrodynamic effects tend to mask the seasonal
cycle in phytoplankton biomass except at inshore localities. The model
predictions confirm the field data that indicate that water quality in the
western bay is severely affected while the better flushed eastern region
remains relatively unaffected. Future increases in nutrient loading due to
population pressure are predicted to extend the severely affected region
eastwards. Over most of the bay, algal productivity is N-limited except for
the western margins where nutrients are saturating and light availability
regulates growth. Model hindcasts suggest that system-wide mean algal
production has increased by a factor of ten since European settlement.
Mapping of coastal ecosystems and halophytes (case study of Abu Dhabi, United Arab Emirates)
Authors: Böer Benno , Gliddon Derek
Published: August 2004

A survey of the coastal zone of Abu Dhabi identified 22 halophytes of which
nine are tolerant to inundation by seawater. A preliminary assessment
suggested that 3.550 km2 of saline land with a complete
absence of natural vegetation was potentially suitable for the development of
sustainable agro-ecosystems with halophyte crops and seawater irrigation. Such
development plans, however, require the implementation of environmental impact
assessments. The inter-tidal plant communities need special protection, as
they are fragile, and economically and ecologically valuable.
Parasites of Antarctic fishes: Monogenea, Copepoda and Acanthocephala
Authors: Rohde Klaus , Ho Ju-Shey , Smales Lesley , Williams Richard
Published: August 2004

The body surface, mouth, gills, internal organs and tissues of 368 teleost
fish of 26 species from Prydz Bay, Heard Island, Macquarie Island, Davis
Station and Casey Station in Antarctica were examined for parasites. At least
eight species of Monogenea, seven species of Copepoda, and five or six species
of Acanthocephala were recorded. Overall, the fauna of Monogenea and Copepoda
of Antarctic fish is much poorer than that of lower latitudes, and there are
fewer species of Gyrodactylidae relative to other Monogenea than at higher
northern latitudes. Abundance and species richness of Acanthocephala are
relatively high.
Extra keyword: species diversity.
Mangrove vegetation: an evolutionary perspective
Authors: Saenger P.
Published: August 2004

The world-wide occurrence of mangrove vegetation and the modern floristic
divergence between the Indo–Pacific and the Atlantic mangroves, can only
be explained by historical processes, in that the composition of the modern
mangrove flora at any one location, while subject to present-day climatic and
geographical conditions, is largely relict. Although several interpretations
have been offered to relate mangrove distributions to past events, none has
been universally accepted. What is explored here, is that there are several
historical and modern processes which in combination, have resulted in the
present day distribution of mangroves. Evolutionary processes are reviewed
from the fossil record and from the data on continental drift. Next, the
ecological processes that are selectively acting on the various species and
their distributions are examined with particular emphasis on aridity,
temperature and latitudinal attentuation of species. Finally, some modern
anthropogenic processes (e.g. species introductions, over-exploitation and
habitat modification, afforestation) are examined in terms of their effects on
mangrove distribution. As an outcome of these various processes, the modern
mangrove vegetation is analysed particularly in relation to regions of
endemism, vicariance among species, discontinuous distributions, hybridization
and divergence. Finally, some speculation is offered in terms of future trends
and evolutionary possibilities.
Mangal roost selection by the flying-fox Pteropus alecto (Megachiroptera : Pteropodidae)
Authors: Loughland Ronald Anthony
Published: August 2004

A study in an unaltered environment was undertaken to gain baseline data on
habitat requirements of flying-fox (Pteropus alecto). A
survey of the South Alligator River in northern Australia during the dry
season of 1992 located 13 P. alecto roosts. A comparison
of their vegetation, and micro-climate with those of matched control sites
with no flying-fox roosts used traditional Aboriginal knowledge, ground and
air survey and a Geographical Information System. Roost habitat was rare in
the study area, being restricted to riparian mangal vegetation that maintained
a closed canopy throughout the dry season. The location and abundance of
mangal vegetation within range of suitable foraging resources was believed to
be the main factor influencing the distribution and colony size of
P. alecto.
Ecological role of grapsid crabs in mangrove ecosystems: a review
Authors: Lee S. Y.
Published: August 2004

Recent research on Indo–Pacific mangroves has confirmed the significant
role played by grapsid crabs in the structure and function of these
ecosystems. Through the feeding activities of the crabs, large proportions of
organic matter production, i.e. mangrove leaves, are recycled within the
forest. This initial retention of production in the forest refines earlier
estimates of tidal export from the mangroves. Crab-processed organic matter
could also form the basis of a coprophagous food chain involving small
invertebrates, or be re-exported as micro-particulates. Differential
consumption by crabs of mangrove propagules also affects mangrove community
structure by diminishing the relative abundance of species whose propagules
are preferred foods. Bioturbation by the crabs also results in changes in
surface topography, particle size distribution and degree of aeration and,
thus, the concentration of phytotoxins in the substratum. Such changes could
affect growth and production of the mangroves. Growth and reproduction of the
crabs may in turn be influenced by the associated mangrove species, mainly
through the provision of food. The semi-terrestrial and air-breathing habit of
the grapsid crabs probably makes them tolerant of deoxygenation caused by
organic enrichment, but development of the landward mangroves will strongly
affect survival of the crabs.
Reproductive biology of school mackerel (Scomberomorus queenslandicus) and spotted mackerel (S. munroi) in Queensland east-coast waters
Authors: Begg Gavin A.
Published: August 2004

Spatial and temporal spawning patterns of school mackerel
(Scomberomorus queenslandicus) and spotted mackerel
(S. munroi) in Queensland east-coast waters, Australia,
(16˚S to 28˚S), were examined to provide reproductive parameters
required for the management and protection of spawning stocks. School mackerel
spawned along the Queensland coastline from October to January. Female school
mackerel were sexually mature between 401 and 450 mm, and males between 351
and 400 mm LCF (length to caudal fork). In contrast, spotted mackerel spawned
in northern Queensland waters from August to October. Females were between 451
and 500 mm, and males 401 and 450 mm LCF at first maturity. Both species were
found to be dioecious. Differential spawning patterns of school and spotted
mackerel may help the species coexist and maintain the integrities of the
species and their respective stock structures.
Photosynthetic gas exchange and water use in tropical and subtropical populations of the mangrove Aegiceras corniculatum
Authors: Youssef Tarek , Saenger Peter
Published: August 2004

Photosynthetic gas exchange and stomatal behaviour in the tropical (Darwin:
12°25′S) and subtropical (Ballina: 28°50′S) populations of
the mangrove Aegiceras corniculatum (L.) Blanco were
compared at elevated air temperatures (>32°C) and leaf-to-air vapour
pressure deficit (vpd >25 mbar) with a quantum flux
at, or above, their light saturation capacity (>600 µmol
m-2 s-1). At the lower end of the
tested aridity range, the tropical population showed a less conservative water
use than the subtropical population. As aridity increased, both populations
showed a reduction in stomatal conductance. However, transpiration rates
remained higher in the subtropical population at all times, reducing its
water-use efficiency from that under less arid conditions. At extreme aridity
(temperature >37°C and vpd >35 mbar), the
efficiency of the evaporative cooling of fully exposed leaves was evident in
the leaf-to-air temperature differential which remained minimal in the
tropical population while it increased significantly in the subtropical
population. Aridity tolerance was more pronounced in individuals from the
tropical site than from the subtropical site, as evidenced by a tighter
stomatal control on water use in the tropical population. These data suggest
that the tropical and subtropical populations of
A. corniculatum have different physiological responses
to aridity.
Mortality rate of a cohort of the coral trout, Plectropomus leopardus, in zones of the Great Barrier Reef Marine Park closed to fishing
Authors: Russ Garry R. , Lou Dong C. , Higgs James B. , Ferreira Beatrice P.
Published: August 2004

From 1990 to 1993, samples of coral trout,
Plectropomus leopardus, were collected at two coral
reefs closed to fishing since 1987 in the central Great Barrier Reef (GBR).
The age structure was dominated by a strong cohort which settled in early 1984
and which accounted for 54%, 45%, 42% and 36% of
the experimental hook-and-line catches at Glow and Yankee reefs. Catch rates
(fish person-1 hour-1) per age
class per reef per year provide the first reliable estimates of the
exponential rate of mortality of coral trout in zones of the GBR Marine Park
closed to fishing. The annual mortality rate between the ages of 6 and 9 years
was 0.115 (s.e. 0.040) at Glow reef and 0.189 (s.e. 0.100) at Yankee reef. The
annual mortality rate between ages 6 and 9 years was 0.147 (s.e. 0.028) at the
two reefs combined. Age-specific estimates of annual mortality ranged from
0.024 (age 7–8 at Glow) to 0.442 (age 6–7 at Yankee) but were
unreliable because of small sample sizes. This is one of the first estimates
of mortality rate of an exploited species in an area closed to fishing in the
tropics.
Age determination of black bream, Acanthopagrus butcheri (Sparidae), from the Gippsland Lakes of south-eastern Australia indicates slow growth and episodic recruitment
Authors: Morison Alexander K. , Coutin Patrick C. , Robertson Simon G.
Published: August 2004

The age of black bream (Acanthopagrus butcheri) in the
Gippsland Lakes of south-eastern Australia was estimated with high precision
from sectioned otoliths of fish sampled from 1993 to 1996. Ageing techniques
were validated by following the progression of age classes over 4 years.
Correct identification of the first increment was aided by reference to the
position of the subcupular meshwork fibre zone, and age assignment was
confirmed by linear regression analyses of otolith weight against fish age.
The growth of black bream was found to be slower, and their natural life span
longer, than previously estimated from length–frequency distributions
and scale readings. The maximum age recorded was 29 years, with most black
bream 4–9 years old and few fish more than 10 years old. There were
significant differences between the growth rates of males and females. The von
Bertalanffy growth parameters were:
L∞ 54.5 cm FL,
t0 –5.21 years,
K 0.042 year-1 for females and
L∞ 38.2 cm FL,
t0 –3.70 years,
K 0.077 year-1 for males. The
current age structure suggests that recruitment has been episodic since 1981
and low for three recent years in succession.
Annual change in reproductive condition and plasma concentrations of sex steroids in black bream, Acanthopagrus butcheri (Munro) (Sparidae)
Authors: Haddy J. A. , Pankhurst N. W.
Published: August 2004

Changes in gonadosomatic index (GSI), hepatosomatic index (HSI), gonad stage
and plasma concentrations of sex steroids were studied over one year in black
bream (Acanthopagrus butcheri). Black bream have an
annual reproductive cycle with a 3-month spawning season in spring–early
summer. GSI and HSI values were highest in October and May respectively.
Plasma concentrations of oestradiol-17β (E2),
testosterone (T) and 17,20β-dihydroxy-4-pregnen-3-one (17,20βP) were
highest in females in October. Plasma concentrations of
E2 and T were highest in ovulated fish. Concentrations
of 17,20βP were higher in fish undergoing final oocyte maturation (FOM)
than in fish with regressed gonads. In males, plasma concentrations of T and
11-ketotestosterone (11KT) increased in September and remained elevated until
January, but concentrations of 17,20βP did not change with season.
However, 17,20βP concentrations in spermiated fish were higher than in
non-spermiated fish. Daily changes in gonad condition indicated that females
undergo daily cycles of ovarian maturation with ovulation occurring after
midday. Plasma T and 17,20βP concentrations of females were elevated at
midday in association with FOM, but E2 showed no diel
change. In males, partially spermiated fish were dominant in the early morning
and fully spermiated fish at midday. Plasma T, 11KT and 17,20βP
concentrations were low at midnight and reached maximum levels at 0600 hours.
Isopod burrowing in leaves of turtle grass, Thalassia testudinum, in a Mexican Caribbean reef lagoon
Authors: Tussenbroek B. I. van , Brearley A.
Published: August 2004

Isopods (Limnoria simulata, Limnoriidae, Flabellifera)
burrowing in the turtle grass Thalassia testudinum
(Banks ex König) are reported from Puerto Morelos reef lagoon, Mexican
Caribbean. Isopods (maximum length 2.0–4 mm) burrowed in sheaths of
outer foliar leaves of shoots; they bored through the middle leaf tissue and
epidermis of the inner face of the sheath, forming canal systems ~20–50
mm long. Traces of isopod burrowing showed as linear arrays of holes in
seagrass blades, which could be observed in the field. Isopods used the
burrows for reproduction, and on many occasions two adults were found together
in one canal system. Frequency of infestation in
T. testudinum varied throughout the reef lagoon and was
highest in a shallow protected coastal zone, where ~50% of the shoots
had isopod burrows in their sheaths. Infestation was lower
(20–30% shoots with damaged sheaths) in mid-lagoon beds, and
minimal in wave-exposed back-reef areas. The distribution of infested shoots
was patchy. Where the degree of infestation was high,
T. testudinum shoots showed reduced blade growth.
Resumen. Se registra la presencia de isópodos
(Limnoria simulata; Flabellifera : Limnoriidae) que
excavan el pasto marino Thalassia testudinum (Banks ex
König) en la laguna arrecifal de Puerto Morelos, en el Caribe mexicano.
Los isópodos de Puerto Morelos (longitud máxima: 2.0–4.0
mm) excavan las vainas de las hojas exteriores de los grupos foliares (haces),
a través del tejido medular y la epidermis del lado interior de la
vaina, formando sistemas de canales de 20 a 50 mm de longitud. En el campo,
los rastros de las excavaciones aparecen como arreglos lineales de agujeros en
las láminas del pasto. Los isópodos utilizan las excavaciones
para reproducirse, y en varias ocasiones se encontraron dos adultos juntos en
un sistema de canales. La frecuencia de infestación en
T. testudinum varió dependiendo del lugar en la
laguna, siendo mayor en una zona costera protegida, donde 50% de los
haces contenían isópodos. Los valores intermedios de
infestación (20–30% de los haces) se encontraron en la
zona media de la laguna, mientras que la infestación fue mínima
en áreas cercanas al arrecife coralino, expuestas al oleaje. La
distribución de los haces infestados de isópodos fue desigual, y
en parches con altos niveles de infestación
T. testudinum mostró un crecimiento reducido.
Effect of capture, confinement and repeated sampling on plasma steroid concentrations and oocyte size in female striped trumpeter Latris lineata (Latrididae)
Authors: Morehead D. T.
Published: August 2004

Wild female striped trumpeter were caught during the spawning season to
examine the effect of capture, confinement and repeated handling on
reproductive function. Blood and ovarian samples were obtained from 5 females
within 10 minutes of capture and from a pool of female fish
(n = 17), including the original 5, that were
sampled regularly from Day 2 to Day 13 after capture. Plasma concentrations of
cortisol, testosterone (T), 17β-oestradiol (E2) and
17,20β-dihydroxy-4-pregnen-3-one (17,20βP) were measured by
radioimmunoassay. Four of the 17 fish ovulated and a small volume of eggs was
obtained by hand stripping. Mean oocyte size did not change significantly,
although there was a general trend toward decreasing oocyte diameters over
time. Plasma concentrations of T and E2 decreased
significantly after capture, and remained low thereafter. Concentrations of
17,20βP remained unchanged apart from a decrease on Day 13. Cortisol
concentrations significantly increased after capture and remained elevated
until Day 5, with subsequent elevations on Days 7 and 9. These results suggest
that the stress of capture, confinement and repeated handling inhibits the
ovarian production of T and E2 but not 17,20βP and
arrests oocyte development at all but the most advanced stages.
The shark genus Carcharhinus Blainville, 1816 (Chondrichthyes : Carcharhinidae) in Argentine waters
Authors: Chiaramonte Gustavo E.
Published: August 2004

The purpose of this contribution is to review the species of the shark genus
Carcharhinus found along the coast of Argentina. New
southern limits for the distribution of the genus are given for the western
South Atlantic. The presence of Carcharhinus leucas
(Valenciennes, 1839) is recorded for the first time on the Province of Buenos
Aires coast. New evidence is given which confirms the presence of
Carcharhinus brachyurus(GÜnther, 1870) in the area.
Carcharhinus plumbeus (Nardo, 1827) is known from only a
single Argentine record. Carcharhinus longimanus (Poey,
1861) has been recorded from oceanic waters offshore of Argentina, but has not
been taken from continental shelf waters.
Resumen. En éste trabajo se revisan las especies
de tiburones del género Carcharhinus encontradas
en la costa de la Argentina. Nuevos límites septentrionales para la
distribución de las especies del género en el Atlántico
Sudoccidental son presentados. Se refiere por primera vez la presencia de
Carcharhinus leucas (Valenciennes, 1839) para la costa
de la Provincia de Buenos Aires. Se presenta nueva evidencia que confirma la
presencia de Carcharhinus brachyurus (GÜnther,
1870) en el área. Carcharhinus plumbeus (Nardo,
1827) ha sido citado una sóla vez para Argentina.
Carcharhinus longimanus (Poey, 1861) ha sido registrado
en aguas oceánicas frente a la plataforma de Argentina, pero no en
aguas sobre la plataforma continental.
Inferring spawning migrations of orange roughy (Hoplostethus atlanticus) from spawning ogives
Authors: Francis R. I. C. C. , Clark M. R.
Published: August 2004

Orange roughy (Hoplostethus atlanticus) occurs
throughout New Zealand waters at depths between 700 and 1500 m. Most spawning
occurs in a few localized aggregations in winter and it appears that fish
migrate substantial distances (hundreds of kilometres) to and from these
aggregations. However, there is no direct evidence of migration. Indirect
evidence of migration of females is presented in the form of trends in
L50, the mid point of the spawning
ogive (i.e. the length at which 50% of mature females are spawners).
Data from 21 research surveys carried out between March and August over an
eleven-year period show consistent geographical trends in
L50 on the east coast and the
Chatham Rise. L50 was consistently
low (28–32 cm) near major spawning grounds and increased to high values
(>34 cm) far from these grounds. These trends increase the knowledge of
orange roughy spawning migrations in two important fishing areas.
Comparison of catches taken in dual-mesh beach seines of two different lengths
Authors: Vanderklift M. A. , Jacoby C. A. , Horwitz P.
Published: August 2004

This study examined the species composition and size structure of fish and
macro-invertebrates captured by two dual-mesh beach seines of different
lengths. Both nets captured small fish, large fish and juveniles. The longer
net appeared to be the best choice as a sampling tool, but support for this
choice was not strong. The assemblages caught by the two nets differed, but
these differences did not mask overall spatial and temporal patterns in
assemblage composition. The longer seine caught more species, but estimates of
total densities for all individuals and densities of three common,
commercially important fish species did not differ consistently between the
two nets. Comparisons and generalizations based on studies that use different
types of seines should be interpreted cautiously because design features may
influence results in inconsistent and unpredictable ways.
Short cyst-dormancy period of an Australian isolate of the toxic dinoflagellate Alexandrium catenella
Authors: Hallegraeff G. M. , Marshall J. A. , Valentine J. , Hardiman S.
Published: August 2004

Cyst beds of Alexandrium catenella (a causative organism
of Paralytic Shellfish Poisoning) are widespread in New South Wales coastal
and estuarine waters (temperature range 13–25˚C). Cysts produced by
cultured isolates exhibited dormancy periods at 17˚C as short as
28–55 days. This contrasts with the usually longer dormancy requirements
of temperate populations of A. catenella from Japan (97
days at 23˚C) and of A. tamarense from Cape Cod or
British Columbia. With some Australian cysts, a 1-h temperature increase from
17˚ to 25˚C (equivalent to summer heating of shallow estuaries)
improved germination success (up to 100% germination achieved after 98
days), but cold–dark storage did not produce the lengthened dormancy
requirements that have been reported overseas for overwintering temperate cyst
populations. The significance of this finding is that different geographic
isolates of the same dinoflagellate taxon can have different cyst dormancy
requirements which play different ecological roles (overwintering strategy
v. rapid cycling between benthos and plankton).
Gill-net mesh selectivity of dusky sharks (Carcharhinus obscurus) and whiskery sharks (Furgaleus macki) from south-western Australia
Authors: Simpfendorfer Colin A. , Unsworth Philip
Published: August 2004

Gill-net mesh selectivity parameters were estimated for
C. obscurus and F. macki from
catches of an experimental net composed of seven panels of mesh ranging in
size from 12.7 cm to 21.6 cm. A maximum-likelihood model was used to fit a
gamma distribution to length data from each of the different-sized meshes.
Mesh selectivity parameters for the gilled-only data set were
θ1 =126.90 and θ1
=20253, and for the data set including gilled and non-gilled sharks
θ1 =130.13 and θ1
=29237. The advantages of the parameters from each of these data sets are
discussed. Mesh-selectivity parameters for F. macki were
θ1 =173.70 and θ2
=26415. The exclusion of data from the two largest mesh sizes, which
had much lower catch rates than the other mesh sizes, did not significantly
change the parameter estim- ates. Catch rates from the panels in the
experimental net that correspond to those used by the commercial gill-net
fishery in south-western Australia were compared and no significant
differences were found.
By-catch of sharks in Patagonian coastal trawl fisheries
Authors: Molen Silvina Van Der , Caille Guillermo , González Raúl
Published: August 2004

In coastal Patagonia, Argentina, an unknown number of species of sharks are
frequently caught in bottom-trawl nets. Between 1993 and 1996, 454 trawls by
Patagonian coastal fisheries (41˚–51˚S) were analysed; 264
included sharks. Of the seven species of sharks caught, the most frequent was
the smoothhound Mustelus schmitti, mainly in
Bahía Engaño (off Chubut). The argentine angelshark
(Squatina argentina) and the tope
(Galeorhinus galeus) were common in the north of
Patagonia, the piked dogfish (Squalus acanthias) in the
central zone, and the narrowmouthed catshark
Schroederichthys bivius in the south. The broadnose
sevengill shark (Notorhynchus cepedianus) was rarely
caught. A single basking shark (Cetorhinus maximus) was
caught in San Matías Gulf (off Río Negro). Although undesirable,
the by-catch of sharks is growing as a result of the increase in the fishing
activities of the region, and the sustainability of the shark populations in
Patagonian coasts is a matter of concern.
Resumen. En las costas de Patagonia, Argentina, un
número desconocido de especies de tiburones son frecuentemente
capturados en las redes de arrastre de fondo. Entre 1993 y 1996 se analizaron
a bordo 454 lances de pesca en las pesquerías costeras de Patagonia,
entre los 41 y 51˚S, y en 264 de ellos se registraron capturas de
tiburones. De las siete especies de tiburones capturadas el mas frecuente fue
el gatuzo Mustelus schmitti, principalmente en
Bahía Engaño, frente a las costas de Chubut. El pez ángel
Squatina argentina y el cazón vitamínico
Galeorhinus galeus fueron comunes en el norte de
Patagonia, el cazón espinoso Squalus acanthias en
la zona central, y el tiburón pintarroja
Schroederichthys bivius en el sur. El tiburón
gatopardo Notorhynchus cepedianus resultó una
especie rara en las capturas. En el Golfo San Matías, frente a las
costas de Río Negro, se capturó un ejemplar de tiburón
peregrino Cetorhinus maximus. Aunque no deseadas, las
capturas de tiburones están aumentando debido al incremento de las
actividades pesqueras en la región, y la sustentabilidad de las
poblaciones de tiburones en Patagonia es motivo de creciente
preocupación.
Palabras clave: tiburones, capturas, redes de arrastre,
pesquerías costeras, Patagonia.
Predicting food consumption of fish populations as functions of mortality, food type, morphometrics, temperature and salinity
Authors: Palomares Maria Lourdes D. , Pauly Daniel
Published: August 2004

A large data set of relative food-consumption estimates
(Q/B) of marine and freshwater fish populations
(n = 108 populations, 38 species) is documented
and used to derive a predictive model for Q/B, using
asymptotic weight, habitat temperature, a morphological variable and food type
as independent variables. Salinity is shown to have no effect on
Q/B in fish well adapted to fresh or salt water (other
things being equal), while mortality (Z), has a strong,
positive effect on Q/B and on gross food-conversion
efficiency (defined by GE =
Z/(Q/B)), by affecting the ratio
of small:large fish. The empirical models thus derived should be useful for
parameterization of trophic models of ecosystems and similar applications.
Can shark resources be harvested sustainably? A question revisited with a review of shark fisheries
Authors: Walker Terence I.
Published: August 2004

Sharks and other chondrichthyans are often described as long lived, slow
growing and producing few offspring. These biological characteristics,
together with the common assumption that recruitment is directly related to
stock, and pessimistic stock prognoses obtained from application of
demographic analysis, have led to doubts that sharks can be harvested
sustainably. Developed over the past 40 or so years from studies of only a few
shark species, these doubts have been reinforced by declining catch rates in
industrial, artisanal and recreational fisheries and in fishing programmes
designed to reduce the risk of sharks attacking humans at bathing beaches.
However, more recent studies and application of modelling techniques allowing
for density-dependent responses to the effects of stock reduction indicate
that shark stocks can be harvested sustainably and, if carefully managed, can
provide very stable fisheries. It is now understood that some species (such as
Galeorhinus galeus,
Carcharhinus plumbeus,
Carcharodon carcharias and several species of dogfish)
have low productivity, whereas other species (such as
Mustelus antarcticus,
Rhizoprionodon terraenovae,
Sphyrna tiburo and
Prionace glauca) have higher productivity. This paper
reviews the use of shark products, the effects of fishing on shark populations
of the world, and recent developments in assessment of shark fishery stocks.
Effects of high irradiance and iron concentration on pigment and fatty acid composition in the cyanobacterium Microcystis aeruginosa
Authors: Walsh Kathryn , Jones Gary J. , Dunstan R. Hugh
Published: August 2004

Microcystis aeruginosa Kuetzing emend. was exposed to
sunlight and artificial illumination at low (1 µM) and high (31
µM) iron concentrations over a 9 h period. With sunlight and low iron,
cellular carotenoid and chlorophyll a concentrations decreased linearly with
time, and membrane polyunsaturated fatty acids were reduced after 9 h. With
sunlight and high iron, there was near-complete loss of all pigments and
reduced concentrations of all major fatty acids within 3 h, presumably due to
photooxidation; almost all phytol, poly- and monounsaturated fatty acids were
absent after 9 h exposure in the high iron medium, indicating total
destruction of membranes by iron-enhanced photooxidation. Although caution is
required in extrapolating results from laboratory grown cultures to field
populations, it is conceivable that high irradiance can influence the
composition of cyanobacterial membranes during natural surface blooms. The
subsequent survival and regeneration of cyanobacterial cells may be affected
under the high iron concentrations which can occur in Australian inland lakes
and rivers.
Shark control: experimental fishing with baited drumlines
Authors: Dudley S. F. J. , Haestier R. C. , Cox K. R. , Murray M.
Published: August 2004

Protective gill-nets (shark nets) have been successful in reducing the
frequency of shark attacks on the coast of KwaZulu-Natal (KZN), South Africa,
since 1952. This is achieved primarily through a local reduction in numbers of
large sharks. Yet the nets are non-selective in terms of shark species caught
and take a by-catch of dolphins, sea turtles, batoids and teleosts. Baited
lines, or drumlines, as used in the Queensland shark control programme, were
tested as possible alternatives to gill-nets. They demonstrated greater
species selectivity for sharks and also a reduced by-catch of non-shark
animals. The shark catch included the three species responsible for most shark
attacks on the KZN coast, Carcharhinus leucas,
Galeocerdo cuvier and
Carcharodon carcharias. The probability of the bait
being scavenged, or a shark being caught, was modelled in relation to a number
of physical environmental factors. Although there was insufficient variability
in the effort data for a quantitative comparison of catch rates between nets
and drumlines, the results suggested that an optimal solution may be to deploy
a combination of nets and drumlines.
Misting of Tomato Plants Improves Leaf Water Status but not Leaf Growth
Authors: Stirzaker R. J. , Hayman P. T. , Sutton B. G.
Published: August 2004

Field and laboratory experiments were carried out to determine whether
modification of the aerial environment in a hot climate would improve the leaf
growth rate and ultimately the yield of well- irrigated processing tomatoes,
Lycopersicon esculentum Mill. cv. UC82B. In the field,
the transpiration rate was modified by frequent applications of a fine mist.
Misting reduced the diurnal fall in leaf water potential by up to 0.5 MPa, but
had no effect on weekly vegetative growth or fruit yield, compared to a
control treatment which was not misted but had accurately managed drip
irrigation. To investigate these processes further, we studied the
relationship between leaf water status and leaf growth in the laboratory using
equipment in which a pot is placed inside a pressure chamber, with the leaves
enclosed in a cuvette. Immediately following a misting event, both the
hydrostatic pressure of the leaf xylem and the leaf expansion rate increased.
The increase in leaf expansion rate was sustained for about 10 min and then
fell below the pre-misted rate so that the net effect of a misting event on
leaf expansion was small or nil. When an elevated leaf water status was
sustained by pressurising the soil for over an hour, there was only a
transient increase in leaf growth, and leaf growth stopped after the pressure
was removed. Both in the laboratory and field, the overall leaf or vegetative
growth was not sensitive to rapid fluctuations in leaf water status. The
implication is that, if sufficient attention is paid to managing the root zone
of crops, the more expensive and less efficient modification of the shoot
environment is unnecessary.
Influence of Periodic Fluctuations in Root Environment on Adaptation to Salinity in Sorghum bicolor
Authors: Amzallag G. Nissim
Published: August 2004

In Sorghum bicolor (L.) Moench, a 3-week exposure to 75
mM NaCl induced the ability to grow at 300 mm NaCl, a lethal concentration for
non-pretreated plants. This property was defined as adaptation to salinity.
The chemical composition of the root medium was periodically modified during
the 3-week maturation of the adaptation response. Two daily 1-h interruptions
of the salinisation treatment were sufficient to prevent the initiation of the
adaptation process, while two daily 1-h modifications of the external NaCl
concentration only disturbed its completion. Moreover, the effect of a short
interruption in the salinisation treatment depended on the time of day it
occurred. The rate of growth was not directly influenced by the water content
or the amount of Na+ ions accumulated in the shoot; it
appears to be a function of the mode of response of the plant to salinity. It
is concluded that the nature of the plant response to salinity is controlled
by the roots, which display a circadian fluctuation in sensitivity to the
ionic and osmotic components of the soil environment.
The Effect of Plant Size on Wheat Response to Agents of Drought Stress. I. Root Drying
Authors: Blum A. , Sullivan C. Y.
Published: August 2004

Plant size has long been implicated in plant response to drought stress. This
study is a first in a series of two intended to examine the effect of plant
size on plant performance under the effect of various agents of drought
stress. Variable plant size (in terms of plant height and shoot biomass)
independent of genetic background effects was experimentally achieved using
rht (tallest),
Rht1 and
Rht2 (medium) and
Rht3 (shortest) homozygous height
isogenic lines of spring wheat (Triticum aestivum cv. Bersee).
Top-root drying is a common stress condition when the top soil dries in the
field. In this experiment wheat was grown in hydroponics system in long PVC
tubes. Stress was applied by allowing the top (40 cm) roots to dry throughout
most of the growing season while the remaining roots were immersed in the
nutrient solution. Average seasonal top-root water potential was reduced from
–0.097 MPa in the controls to –1.93 MPa under stress. This stress
condition caused a reduction in shoot biomass while it increased total root
length. There was a general progressive increase in leaf diffusive resistance
under the treatment as plants became larger. This stomatal closure could not
be accounted for by reduction in leaf water potential. In fact, leaf turgor
increased as stomatal diffusive resistance increased with increasing plant
size, leading us to conclude that stomatal closure was the primary response to
top-root drying, followed by turgor maintenance possibly as a result of a
non-hydraulic signal produced by the drying top-roots. Smaller plants were
affected relatively less than were larger plants by this stress condition in
terms of stomatal closure, plant height, tillering and shoot biomass
reduction. Grain yield per plant was actually increased by stress in the
smallest plants while it was unaffected by stress in the larger plants. It is
concluded that the smallest plants were the most resistant to top-root drying
but absolute biomass and yield under this stress condition was the greatest in
the largest plants because of their relatively greater potential.
The Effect of Plant Size on Wheat Response to Agents of Drought Stress. II. Water Deficit, Heat and ABA
Authors: Blum A. , Sullivan C. Y. , Nguyen H. T.
Published: August 2004

Plant size has long been implicated in plant response to drought stress. This
study is the second in a series of two intended to examine the effect of plant
size on plant performance under the effect of various agents of drought
stress. Variable plant size (in terms of plant height and shoot biomass)
independent of genetic background effects was experimentally achieved using
rht (tallest),
Rht1 and
Rht2 (medium) and
Rht3 (shortest) homozygous height
isogenic lines of spring wheat (Triticum aestivum)
cultivars Bersee and April-Bearded.
Plants were grown in hydroponic culture in the growth chamber. In the first
experiment, juvenile plants were challenged by osmotic stress using
polyethylene glycol (PEG) in the nutrient solution giving a water potential of
–0.55 MPa. The control nutrient solution was at –0.05 MPa. Plant
growth, shoot biomass, leaf area, relative water content (RWC) and osmotic
adjustment (OA) were measured. In the second experiment, effects on growth
rate of chronic heat stress and abscisic acid (ABA) in the root medium of
juvenile plants were evaluated.
Potential plant size as determined by shoot biomass in the controls at 25 days
after emergence was greatest in rht, medium in
Rht1 and
Rht2, and smallest in
Rht3 genotypes. Potential growth
rate and leaf area were greater in plants of larger potential biomass
(rht) than in plants of smaller potential biomass
(Rht3). Growth reduction by
osmotic stress was inversely related to plant size, while the extent of
osmotic adjustment during osmotic stress was directly related to plant size.
RWC did not vary with plant size. Relative growth reduction by heat stress and
by ABA also decreased in smaller plants. ABA did not alleviate the depressing
effect of heat on growth.
Despite the greater stress tolerance of smaller
(Rht3) plants, the absolute growth
and biomass of large (rht) plants under stress
conditions was always better than that of smaller plants. The results of these
series of experiments suggest that greater stress tolerance of small plants is
derived from their relatively smaller size and slower growth rate.
Consequently, we conclude that growth under stress is sustained by potential
growth rate and plant size of the genotype when stress is mild and by plant
tolerance (even at the expense of potential growth rate and size) when stress
is more severe.
Sites of Action of Copper in the Photosynthetic Apparatus of Maize Leaves: Kinetic Analysis of Chlorophyll Fluorescence, Oxygen Evolution, Absorption Changes and Thermal Dissipation as Monitored by Photoacoustic Signals
Authors: Ouzounidou Georgia , Moustakas Michael , Strasser Reto J.
Published: August 2004

Fluorescence, absorbance and photoacoustic methods were used to examine
in vivo various functional aspects of the photochemical
apparatus of maize leaves exposed to different Cu concentrations. The primary
photochemistry of a dark adapted leaf was less affected in the presence of Cu,
while in a light-adapted leaf the photochemical events were severely impaired
by Cu. Analysis of the characteristics of chlorophyll fluorescence induction
revealed that the primary target of Cu stress involved the PSII reaction
centre in its ability to adapt to high light conditions. Denaturation of PSII
occured at 80 µM Cu resulting in a significant loss of PSII-mediated
electron transport under continuous light and a strong inhibition of
O2 evolution. It was also observed that PSI
photochemistry, as probed by the photochemical energy storage in far-red light
and the kinetics of P700 photooxidation by strong far-
red light, was more tolerant to Cu compared to the PSII activity. Moreover, in
Cu-exposed leaves irradiated with high intensity light, the in vivo heat
emission yield increased due to the Cu deactivation of photosynthetic energy
conservation. Heat release was well correlated with changes in non-
photochemical quenching. Copper gradually prevents the adaptation process from
a dark-adapted to a light-adapted state with the consequence that all observed
photosynthetic activity criteria under steady state conditions in the light
become more inefficient.
Cortical Intracellular Electrical Potential in Roots of Unstressed and Stressed Sunflower Seedlings. I. Dependence on Water Status
Authors: Cortes P. M.
Published: August 2004

The intracellular electrical potential
(Ec) was measured with a
microelectrode in cortical cells of intact roots of sunflower
(Helianthus annuus) seedlings subjected to differing
levels of water stress and illumination. Water stress was rapidly imposed and
relieved by lowering and raising the level of nutrient solution in a tank
which contained all the seedling roots except the lateral root in which
Ec was measured. The base value of
Ec for unstressed, illuminated
seedlings was –120 mV. When placed in the dark, a small reversible
depolarisation of approximately 10 mV could be measured in roots of seedlings
grown under low levels of radiation but was not evident in seedlings grown
under high levels of radiation. The imposition of and relief from extreme
water stress (leaves and apex severely wilted) resulted in a reversible
depolarisation of approximately 50 mV. The effect of water stress was greatly
reduced by the presence of sucrose and glucose in the nutrient solution
perfusing the 30 mm portion of the lateral root in which
Ec was measured. It appears likely
that the variation in potential was mediated by a reduction in the supply of
photosynthate to the roots.
The Response of Xanthophyll Cycle-dependent Energy Dissipation in Alocasia brisbanensis to Sunflecks in a Subtropical Rainforest
Authors: Barker David H. , Logan Barry A. , III William W. Adams , Demmig-Adams Barbara
Published: August 2004

The photosynthetic responses of leaves of
Alocasia brisbanensis (F.M. Bailey) Domin (Araceae) to
sunflecks were monitored via chlorophyll fluorescence beneath the canopy of a
subtropical rainforest in Australia. Additionally, the size and conversion
state of the xanthophyll cycle were determined. Acclimation to understory
environments that regularly experienced sunflecks involved small increases in
the size of the xanthophyll cycle pool in comparison to understory plants that
never received sunflecks. In understory plants that regularly experienced
sunflecks the rate of photochemistry and the level of xanthophyll
cycle-dependent energy dissipation closely tracked changes in incident PFD.
Subsequent to the first sunfleck plants tended to retain their pool of
xanthophyll cycle carotenoids as the deepoxidised forms (antheraxanthin and
zeaxanthin) throughout the day. Retention of these deepoxidised forms
apparently allows the trans-thylakoid membrane proton gradient to engage and
disengage dissipation rapidly in response to a sunfleck, thereby mitigating
photooxidative damage and ensuring a rapid return to efficient light
utilisation via photosynthesis in limiting light. Our results were also in
agreement with previous studies that demonstrated a requirement for light
activation of photosynthesis.
Effect of the Duration and Intensity of Heat Shock During Grain Filling on Dry Matter and Protein Accumulation, Technological Quality and Protein Composition in Bread and Durum Wheat
Authors: Corbellini M. , Canevar M.G. , Mazza L. , Ciaffi M. , Lafiandra D. , Borghi B.
Published: August 2004

High temperatures occurring during grain filling are known to affect wheat
grain yield and quality considerably. In this paper we report the results of
experiments carried out with two cultivars of bread wheat
(Triticum aestivum L.) and two cultivars of durum wheat
(Triticum durum Desf.). The plants, cultivated in pots,
were subjected to 13 heat treatments (temperature up to 40°C) differing in
duration and timing and starting 7 days after anthesis. Heat treatments were
applied by temporary transfer of the pots to a glasshouse where the
temperature rose to 40°C as a consequence of solar radiation for periods
ranging from 5 to 30 days. The applied heat shocks substantially affected dry
matter and protein accumulation in the different parts of the plant. Early
heat shock (5 days with a total of 18 h of temperature in the range
35–40°C) caused a small reduction of kernel mass and no effect on
protein per kernel; the damage was greater in the central and in the final
stage of grain filling. Plants subjected to a progressive increase of
temperature, or to an early heat shock, acquired thermotolerance to further
heat shocks. Continuous exposure to very high temperatures from 27 days after
pollination to maturity did not negatively affect grain yield and it
facilitated the remobilisation of nitrogen from vegetative to reproductive
organs. Rheological properties were severely affected by heat shocks at all
stages of grain filling: 5 days of heat shock were sufficient to reduce mixing
tolerance by 40–60%. These variations in rheological properties
were accompanied by modification of the level of protein aggregation: soluble
polymeric proteins and low molecular weight gliadins progressively increased
according to the intensity of the stress, while insoluble polymeric proteins
decreased.
Our experiments, carried out in conditions close to the Mediterranean climate,
indicate that the occurrence of very high temperature in the range
35–40°C during grain filling substantially affects dry matter and
protein accumulation in the different parts of the plant. The formation of the
complex protein aggregates responsible for positive dough mixing properties is
significantly reduced by very high temperature. When heat shock came late in
grain filling, grain yield and protein concentration were not negatively
affected but a ‘dough weakening’ effect, which may reduce the
commercial value of the production, is to be expected.
Changes in Gene Expression during Drying in a Desiccation-Tolerant Grass Sporobolus stapfianus and a Desiccation-Sensitive Grass Sporobolus pyramidalis
Authors: Gaff D.F. , Bartels D. , Gaff J.L.
Published: August 2004

For the first time in the grasses, a desiccation-tolerant species
(Sporobolus stapfianus) was examined for evidence of
drought-induced changes in gene transcription. Desiccation tolerance (the
ability of this species to recover from a water potential of –540 MPa)
is induced in the resurrection grass during the drying process itself.
Specific mRNA was compared in extracts of air-dry, drying and fully hydrated
leaves by comparisons of the encoded proteins translated
in vitro and partitioned by 2- dimensional
electrophoresis. Forty-one genes, that were not expressed in hydrated leaves,
were transcribed during drying, whereas only 25 novel polypeptides (translated
in vitro) were detected; this suggests that gene
expression was controlled mainly at the transcriptional level, but possibly
also at the translational level.
Leaves of S. stapfianus become desiccation tolerant as
they dry on intact plants with mechanically undisturbed roots, whereas leaves
on plants whose roots have been disturbed die during drying. Complements of
mRNA from live S. stapfianus leaves changed markedly
from full hydration to 70% RWC and to air-dryness; they also differed
markedly from drought-sensitive leaves (on plants with disturbed roots) at
70% RWC and dead air-dry S. stapfianus leaves and
from leaves of the desiccation sensitive grass
S. pyramidalis at the same water contents.
Drought-induced injury could not be attributed to low abundance of mRNA in
either species. Five criteria which might be involved in desiccation tolerance
were applied to specific in vitro proteins of
S. stapfianus; 12 novel proteins correlated with
desiccation tolerance in a least four of the five criteria.