Movement of tagged juvenile tailor (Pomatomus saltatrix) in Moreton Bay, Queensland

Large quantities of tailor, Pomatomus saltatrix, are caught by recreational and commercial fishers in coastal waters off New South Wales and Queensland. Juvenile tailor were subject to increasing fishing mortality in Moreton Bay (Queensland) in the mid 1980s. A tagging programme, involving State Government fisheries biologists and amateur fishing clubs, was established in 1986 to examine the movement, growth rate and fisheries exploitation of juvenile tailor (<270 mm fork length) in Moreton Bay. Of 2173 juvenile tailor tagged in Moreton Bay during February-July and December 1987, 237 were recaptured over a period of 30 months, representing a recapture rate of 11%. This was a high recapture rate compared with those in similar finfish tagging studies carried out in Moreton Bay. The recaptured fish moved relatively short distances (mean plus or minus s.d., 10.2 plus or minus 15.0 km; maximum distance, 85 km). Growth data were unreliable. Estuaries such as Moreton Bay function as nursery areas for tailor prior to their movement onto open surf beaches as adult fish. A legal minimum length for tailor was introduced on the basis of this study.

Fishery biology and management of Protonibea diacanthus (Sciaenidae) aggregations in far Northern Cape York Peninsula waters

The sciaenid Protonibea diacanthus is a large, long-lived predatory fish of inshore northern Australian waters, which forms annual aggregations that are fished extensively by traditional (subsistence) and recreational fishers. There are now widespread concerns that the resource is being overexploited. Indigenous fishers of the Cape York Northern Peninsula Area (NPA) relate that large adult fish (up to 1500 mm total length (TL)) made up the bulk of the catch from the sciaenid aggregations until about 1994. In contrast, sexually mature P. diacanthus comprised only a small component (12 fish out of 270=4.4%) examined in a 1999–2000 sampling programme that was biased towards the largest individuals available. At 790 mm TL, the minimum size at first maturity for female P. diacanthus in this study is much smaller than the 920 mm TL reported previously in Queensland waters. Developing ovaries were observed in specimens sampled from sciaenid aggregations which formed in NPA waters between May and September 2000. However, no fish with ripe or spent gonads were found in the study, so the current timing and location of the spawning season for P. diacanthus in the region remain unknown. Food items observed in the analysis of the diet of P. diacanthus from the NPA included a variety of teleosts and invertebrates. The range of animal taxa represented in the prey items support the description of an ‘opportunistic predator’ attributed to the species. In our sampling, the stomach contents of fish caught during the time of the aggregation events did not differ from those observed at other times of the year. A total of 114 P. diacanthus were tagged and released at aggregation sites during the study period, and 3 fish (2.6%) were subsequently recaptured. The low rate of tag returns from the wild stock tagging programme, both in this study (2.6%) and from recreational fisher tag/release programmes for the sciaenid elsewhere in Queensland (6.5%), were not explained by tag loss nor mortality, given the high retention rate of tags and the zero mortality seen in tank trials. In response to the biological findings from this study, indigenous community councils of the NPA imposed a 2-year fishing moratorium for P. diacanthus. Surveys at aggregation sites in 2002 and 2003 established that much larger fish (mean size 103.5 cm TL) were again present on the grounds, albeit in very low numbers. These recent preliminary results highlight the critical need for continued monitoring and management of the P. diacanthus fishery in the NPA, if prospects for resource recovery are to be realised. The NPA initiative has provided a rare opportunity to negotiate a co-management strategy, based on scientific data and traditional knowledge, for the recovery of a cultural and economically significant fished resource.

Host recognition by a polyphagous lepidopteran (Helicoverpa armigera): Primary host plants, host produced volatiles and neurosensory stimulation

An important question in the host-finding behaviour of a polyphagous insect is whether the insect recognizes a suite or template of chemicals that are common to many plants? To answer this question, headspace volatiles of a subset of commonly used host plants (pigeon pea, tobacco, cotton and bean) and nonhost plants (lantana and oleander) of Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) are screened by gas chromatography (GC) linked to a mated female H. armigera electroantennograph (EAG). In the present study, pigeon pea is postulated to be a primary host plant of the insect, for comparison of the EAG responses across the test plants. EAG responses for pigeon pea volatiles are also compared between females of different physiological status (virgin and mated females) and the sexes. Eight electrophysiologically active compounds in pigeon pea headspace are identified in relatively high concentrations using GC linked to mass spectrometry (GC-MS). These comprised three green leaf volatiles [(2E)-hexenal, (3Z)-hexenylacetate and (3Z)-hexenyl-2-methylbutyrate] and five monoterpenes (α-pinene, β-myrcene, limonene, E-β-ocimene and linalool). Other tested host plants have a smaller subset of these electrophysiologically active compounds and even the nonhost plants contain some of these compounds, all at relatively lower concentrations than pigeon pea. The physiological status or sex of the moths has no effect on the responses for these identified compounds. The present study demonstrates how some host plants can be primary targets for moths that are searching for hosts whereas the other host plants are incidental or secondary targets.

Paropsine beetles (Coleoptera: Chrysomelidae) in south-eastern Queensland hardwood plantations: identifying potential pest species

Paropsine chrysomelid beetles are significant defoliators of Australian eucalypts. In Queensland, the relatively recent expansion of hardwood plantations has resulted in the emergence of new pest species. Here I identify paropsine beetles collected from Eucalyptus cloeziana Muell. and E. dunnii Maiden, two of the major Eucalyptus species grown in plantations in south-eastern Queensland, and estimate the relative abundance of each paropsine species. Although I was unable to identify all taxa to species level, at least 17 paropsine species were collected, about one-third of which have not been previously associated with hardwood plantations. Paropsis atomaria Olivier and P. charybdis Stål were the most abundant species collected in E. cloeziana plantations, while Chrysophtharta cloelia (Stål) and P. atomaria were most commonly collected from E. dunnii. Occasional collections from Corymbia citriodora (Hook.) Hill and Johns, ssp. variegata revealed an additional four species implicated in plantation damage. Abundance and voltinism varied between species and sites. I predict which paropsine species are likely to threaten plantation productivity.

Heritability of reproductive traits and genetic correlations with growth in the black tiger prawn Penaeus monodon reared in tanks

Captive-reared broodstock of the black tiger prawn (Penaeus monodon) have exhibited poor reproductive performance limiting attempts to domesticate this species. The potential for improved reproductive performance was assessed by determining heritabilities of four measures of reproductive performance, their genetic correlations with each other and with growth rate and weight at age. Heritability estimates (h2 ± S.E.) obtained from √ (days to spawn), √ (egg number), √ (nauplii number) and arcsin √ (proportion hatched) were 0.47 ± 0.15, 0.41 ± 0.18, 0.27 ± 0.16, and 0.18 ± 0.16, respectively. Estimates of genetic correlations between reproductive traits and weight at age, or growth rate were less than 0.5 except for √ (egg number) and weight at 54 weeks (0.93 ± 0.19) and √ (egg number) and 16-54-week growth (0.63 ± 0.29).

Growth and carcass characteristics of cast-for-age Merino ewes fed sorghum-based feedlot diets

Grain feeding low bodyweight, cast-for-age (CFA) sheep from pastoral areas of eastern Australia at the end of the growing season can enable critical carcass weight grades to be achieved and thus yield better economic returns. The aim of this work was to compare growth and carcass characteristics for CFA Merino ewes consuming either simple diets based on whole sorghum grain or commercial feed pellets. The experiment also compared various sources of additional nitrogen (N) for inclusion in sorghum diets and evaluated several introductory regimes. Seventeen ewes were killed initially to provide baseline carcass data and the remaining 301 ewes were gradually introduced to the concentrate diets over 14 days before being fed concentrates and wheaten hay ad libitum for 33 or 68 days. Concentrate treatments were: (i) commercial feed pellets, (ii) sorghum mix (SM; whole sorghum grain, limestone, salt and molasses) + urea and ammonium sulfate (SMU), (iii) SMU + whole cottonseed at 286 g/kg of concentrate dry matter (DM), (iv) SM + cottonseed meal at 139 g/kg of concentrate DM, (v) SMU + virginiamycin (20 mg/kg of concentrate) for the first 21 days of feeding, and (vi) whole cottonseed gradually replaced by SMU over the first 14 days of feeding. The target carcass weight of 18 kg was achieved after only 33 days on feed for the pellets and the SM + cottonseed meal diet. All other whole grain sorghum diets required between 33 and 68 days on feed to achieve the target carcass weight. Concentrates based on whole sorghum grain generally produced significantly (P < 0.05) lower carcass weight and fat score than pellets and this may have been linked to the significantly (P < 0.05) higher faecal starch concentrations for ewes consuming sorghum-based diets (270 v. 72 g/kg DM on day 51 of feeding for sorghum-based diets and pellets, respectively). Source of N in whole grain sorghum rations and special introductory regimes had no significant (P > 0.05) effects on carcass weight or fat score of ewes with the exception of carcass weight for SMU + whole cottonseed being significantly lower than SM + cottonseed meal at day 33. Ewes finished on all diets produced acceptable carcasses although muscle pH was high in all ewe carcasses (average 5.8 and 5.7 at 33 and 68 days, respectively). There were no significant (P > 0.05) differences between diets in concentrate DM intake, rumen fluid pH, meat colour score, fat colour score, eye muscle area, meat pH or meat temperature.

Relative host plant species use by the lantana biological control agent Aconophora compressa (Membracidae) across its native and introduced ranges

Aconophora compressa Walker (Hemiptera: Membracidae) was released in 1995 against the weed lantana in Australia, and is now found on multiple host plant species. The intensity and regularity at which A. compressa uses different host species was quantified in its introduced Australian range and also its native Mexican range. In Australia, host plants fell into three statistically defined categories, as indicated by the relative rates and intensities at which they were used in the field. Fiddlewood (Citharexylum spinosum L.: Verbenaceae) was used much more regularly and at higher densities than any other host sampled, and alone made up the first group. The second group, lantana (Lantana camara L.: Verbenaceae; pink variety) and geisha girl (Duranta erecta L.: Verbenaceae), were used less regularly and at much lower densities than fiddlewood. The third group, Sheena’s gold (another variety of D. erecta), jacaranda (Jacaranda mimosifolia D. Don: Bignoniaceae) and myoporum (Myoporum acuminatum R. Br.: Myoporaceae), were used infrequently and at even lower densities. In Mexico, the insect was found at relatively low densities on all hosts relative to those in Australia. Densities were highest on L. urticifolia, D. erecta and Tecoma stans (L.) Juss. ex Kunth (Bignoniaceae), which were used at similar rates to one another. It was found also on a few other verbenaceous and non-verbenaceous host species but at even lower densities. The relative rate at which Citharexylum spp. and L. urticifolia were used could not be assessed in Mexico because A. compressa was found on only one plant of each species in areas where these host species co-occurred. The low rate at which A. compressa occurred on fiddlewood in Mexico is likely to be an artefact of the short-term nature of the surveys or differences in the suites of Citharexylum and Lantana species available there. These results provide further incentive to insist on structured and quantified surveys of non-target host use in the native range of potential biological control agents prior to host testing studies in quarantine.

Phenotypic and genotypic variation within populations of kikuyu (Pennisetum clandestinum) in Australia.

Experiments at 2 sites in subtropical eastern Australia investigated the variation in agronomic attributes, quality and genetic structure existing within: naturally-occurring populations of kikuyu ( Pennisetum clandestinum) from within Australia; selections produced from the treatment of Whittet seed with mutagenic chemicals; and available cultivars. Runners were collected from coastal areas extending from Western Australia to the Atherton Tableland in north Queensland. One experiment evaluated 10 mutagenic selections and 4 cultivars in a lattice design and the other evaluated 12 ecotypes and 3 cultivars in a randomised block design. The experimental unit was single plants, which were sown on a 1.5 m grid into a weed-free seed-bed (Mutdapilly) or a killed kikuyu stand (Wollongbar), both of which were kept clear of weeds and other kikuyu plants for the duration of the experiments. Foliage height, forage production and runner yield were assessed. Leaf material was analysed for concentrations of crude protein (CP), acid detergent fibre (ADF) and neutral detergent fibre (NDF) and for in vitro dry matter digestibility (IVDDM) in autumn, winter and spring. DNA was extracted from each plant in the ecotype comparison and subjected to a modified DAF (DNA amplification fingerprinting) analysis to determine the level of genetic relatedness. In the first experiment, none of the mutagenic lines derived from Whittet yielded significantly more or was more digestible than commercial Whittet material, although some selections were superior to the other commercial kikuyu cultivars, Noonan and Crofts, and 'common' kikuyu. However, there were significant differences in plant height and runner expansion. In the second experiment, significant differences in plant height, foliage yield, runner development, and leaf CP, ADF, NDF and IVDDM concentrations were demonstrated between the ecotypes, mutagenic selections and cultivars. There was a 4- to 6-fold difference in plant yield and a 6- to 10-fold difference in runner production between the ecotypes at the 2 sites. Quality of the leaf ranged from 200 to 270 g/kg (CP), from 700 to 770 g/kg (IVDDM), from 170 to 250 g/kg (ADF) and from 470 to 550 g/kg (NDF). Improvements in quality and agronomic attributes were not mutually exclusive. Genetic fingerprint analysis of the kikuyu lines indicated that they formed 2 broad groupings. Most of the regional ecotypes were grouped with 'common' kikuyu as represented by the material collected from Wollongbar, and the Beechmont, Atherton Tableland and Gympie ecotypes were grouped with the registered cultivars Whittet, Noonan and Crofts. Two lines produced by mutagenesis from Whittet remained closely linked to Whittet. These results suggest that there was variation between populations of kikuyu in yield, quality and genetic diversity but that mutagenesis by treating seed with sodium azide and diethylene sulphide did not achieve a significant change in the digestibility of leaf over cv. Whittet.

Complementing biological control with plant suppression: Implications for improved management of parthenium weed (Parthenium hysterophorus L.)

Parthenium hysterophorus L. is a weed of global significance that has become a major weed in Australia and many other parts of the world. A combined approach for the management of parthenium weed using biological control and plant suppression, was tested under field conditions over a two-year period in southern central Queensland. The six suppressive plant species, selected for their demonstrably suppressive ability in earlier glasshouse studies, worked synergistically with the biological control agents (Epiblema strenuana Walker, Zygogramma bicolorata Pallister, Listronotus setosipennis Hustache and Puccinia abrupta var. partheniicola) present in the field to reduce the growth (above ground biomass) of parthenium weed, by between 60–86% and 47–91%, in Years 1 and 2, respectively. The biomass of the suppressive plants was between 6% and 23% greater when biological control agents were present than when the biological control agents had been excluded. This shows that parthenium weed can be more effectively managed by combining the current biological control management strategy with selected sown suppressive plant species, both in Australia and elsewhere.

A comparison of the electrosensory morphology of a euryhaline and a marine stingray

The electrosensory system is found in all chondrichthyan fishes and is used for several biological functions, most notably prey detection. Variation in the physical parameters of a habitat type, i.e. water conductivity, may influence the morphology of the electrosensory system. Thus, the electrosensory systems of freshwater rays are considerably different from those of fully marine species; however, little research has so far examined the morphology and distribution of these systems in euryhaline elasmobranchs. The present study investigates and compares the morphology and distribution of electrosensory organs in two sympatric stingray species: the (euryhaline) estuary stingray, Dasyatis fluviorum, and the (marine) blue-spotted maskray, Neotrygon kuhlii. Both species possess a significantly higher number of ventral electrosensory pores than previously assessed elasmobranchs. This correlates with a diet consisting of benthic infaunal and epifaunal prey, where the electrosensory pore distribution patterns are likely to be a function of both ecology and phylogeny. The gross morphology of the electrosensory system in D. fluviorum is more similar to that of other marine elasmobranch species, rather than that of freshwater species. Both D. fluviorum and N. kuhlii possess 'macro-ampullae' with branching canals leading to several alveoli. The size of the pores and the length of the canals in D. fluviorum are smaller than in N. kuhlii, which is likely to be an adaptation to habitats with lower conductivity. This study indicates that the morphology of the electrosensmy system in.a euryhaline elasmobranch species seems very similar to that of their fully marine counterparts. However, some morphological differences are present between these two sympatric species, which are thought to be linked to their habitat type. (C) 2013 Elsevier GmbH. All rights reserved.

Continuous combined microwave and hot air treatment of apples for fruit fly (Bactrocera tryoni and B. jarvisi) disinfestation

Apples at 24 ± 2 °C were heated in a pilot scale hot air assisted (40 °C) continuous pentagonal microwave system, to evaluate the effectiveness of this treatment on insect mortality (variety Mutsu) and fruit quality (variety Granny Smith). An average temperature of 53.4 ± 1.3 °C at core, bottom and flesh of the apple was recorded at the end of the treatment. One hundred percent mortality of the most tolerant stage of Queensland fruit fly (Bactrocera tryoni, Froggatt) and Jarvis's fruit fly (Bactrocera jarvisi, Tryon), were observed when the Mortality value (M52, equivalent time of isothermal treatment at 52 °C) at the slowest heating point applicable for each experiment was ≥ 50 min and ≥ 37 min, respectively. Results showed that microwave heat treatment is effective for insect disinfestation without any adverse impact on total soluble solids, flesh or peel firmness of the treated apples. The treated apples recorded a significantly higher pH and lower ion leakage than the untreated apples after 3 or 4 weeks. Therefore, the microwave heat treatment has the potential to be developed as an alternative chemical free quarantine treatment against economically significant insect pests. Industrial relevance Hot air assisted microwave heating of fruits and vegetables, is more cost effective compared to vapour heat treatment and ionising radiation for disinfestation of insects. Microwave treatment is environmentally friendly compared to fumigation and chemical treatments. Hot air assisted microwave disinfestation can be performed at farms or centralised pack houses since the capital cost would be comparatively lower than vapour heat or ionising radiation treatments.