Golden Grey Mullet Liza Aurata Research Articles

Reproductive biology of the Golden grey mullet Liza aurata (Risso, 1810) in Bardawil Lagoon, Egypt

Reproductive biology of the Golden grey mullet Liza aurata (Risso, 1810) in Bardawil Lagoon, Egypt

The osteology of the golden grey mullet Liza aurata (Teleostei: Mugiliformes: Mugilidae) including interactive three-dimensional reconstructions.

Grey mullets are remarkably characterized by their overall uniform external morphology. Identifying species as well as positioning the Mugiliformes in a phylogenetic context is rather difficult. Most recently they were placed in the newly erected Ovalentaria, but more detailed relationships to potential sister taxa were not resolved. Studying the internal morphology, especially the osteology, might provide new insights into the evolution of the Mugiliformes as well as help clarify their phylogenetic position within the Ovalentaria. A detailed osteology of the golden grey mullet Liza aurata is presented. The use of cleared and stained specimens allowed for a complete examination of bony and cartilaginous structures, and a 3D reconstruction from a μCT data set provided additional information on the positional relationships of the bones. Following this, the data obtained were compared with different mugilid species, particularly with the flathead grey mullet Mugil cephalus. Several differences between these species could be identified, such as the position of the basisphenoid, the shape of the hyomandibular and the composition of the branchial arches. These characters might help in understanding the evolutionary changes happening within the mugiliforms and will provide the basis to study this taxon in detail, finally allowing the reconstruction of the body plan of grey mullets.

Experimental Rearing of the Golden Gray Mullet Liza Aurata (Risso, 1810) in a Recirculating System at the Black Sea

Abstract Recirculating Aquaculture Systems (RAS) used in aquatic research and production are a viable alternative to traditional open-sea mariculture. The rearing of marine living resources in controlled environments is one of NIMRD’s constant concerns. Golden gray mullet Liza aurata (Risso, 1810) is spread in the Mediterranean, Black and Caspian Seas, as well as along the Atlantic coast, and culture in extensive and semi-intensive enclosures has been practiced worldwide for centuries, especially in the Far East and the Mediterranean, reaching a global production of 134,329 tons in 2010. The species’ potential for aquaculture is enhanced by its eurihalyne and eurithermal adaptability, allowing it to grow in a variety of ecosystems. The biological material used for the experiment was represented by golden gray mullet fingerlings fished using the beach seine from the Black Sea. They were monitored for health state, growth rythm (mean length and weight determinations), behavior under RAS conditions, survival rate and overall adaptability. The growth of juveniles after 90 days was 89.2% for total length and 246% for mean biomass. Concerning overall adaptability, after approximately one month, the golden gray mullet individuals fully adapted to rearing in the RAS tanks and handling during measurements. Moreover, the food administered (Skretting Classic K) was easily accepted, active feeding behavior being observed even in the presence of NIMRD’s staff. The fish’s health state was good, with no mortalities caused by infections or parasites. The survival rate upon completion of the two monitoring months was 76.66% (23 of the 30 individuals included in the experiment). The preliminary results obtained showed a good adaptability and a normal growth rate, which makes Liza aurata a potential candidate for aquaculture targeting the national and regional market.

Depletion of Essential Fatty Acids in the Food Source Affects Aerobic Capacities of the Golden Grey Mullet Liza aurata in a Warming Seawater Context.

The objective of this study was to evaluate the combined effects of thermal acclimation and n-3 highly unsaturated fatty acids (n-3 HUFA) content of the food source on the aerobic capacities of fish in a thermal changing environment. The model used was the golden grey mullet Liza aurata, a species of high ecological importance in temperate coastal areas. For four months, fish were exposed to two food sources with contrasting n-3 HUFA contents (4.8% ecosapentaenoic acid EPA + docosahexaenoic acid DHA on the dry matter DM basis vs. 0.2% EPA+DHA on DM) combined with two acclimation temperatures (12°C vs. 20°C). The four experimental conditions were LH12, LH20, HH12 and HH20. Each group was then submitted to a thermal challenge consisting of successive exposures to five temperatures (9°C, 12°C, 16°C, 20°C, 24°C). At each temperature, the maximal and minimal metabolic rates, metabolic scope, and the maximum swimming speed were measured. Results showed that the cost of maintenance of basal metabolic activities was particularly higher when n-3 HUFA food content was low. Moreover, fish exposed to high acclimation temperature combined with a low n-3 HUFA dietary level (LH20) exhibited a higher aerobic scope, as well as a greater expenditure of energy to reach the same maximum swimming speed as other groups. This suggested a reduction of the amount of energy available to perform other physiological functions. This study is the first to show that the impact of lowering n-3 HUFA food content is exacerbated for fish previously acclimated to a warmer environment. It raises the question of the consequences of longer and warmer summers that have already been recorded and are still expected in temperate areas, as well as the pertinence of the lowering n-3 HUFA availability in the food web expected with global change, as a factor affecting marine organisms and communities.

Study of Myxosporea (Myxozoa), infecting worldwide mullets with description of a new species.

Existing data on Myxozoa parasites infecting mullets were reviewed. The validity of nine species names was updated. Sixteen species were registered during analysis of original material collected in the Mediterranean, Black, Azov, and Japan Seas in 2004–2005. A new bivalvulid myxozoan parasite, Myxobolus adeli n. sp., was described from the inner organs of the golden grey mullet Liza aurata (Risso, 1810) collected in the Mediterranean (Ebro Delta, Spain), Black Sea (Kerch Strait, Ukraine), and Azov Sea (Genichesk, Ukraine) coastal waters. It is characterized by the presence of elongated, spindle-like cysts 0.5–1.3 mm in size, filled with wide transverse-oval spores about 6.2 × 7.2 × 4.6 μm in size, with two equal polar capsules measuring about 3.0 × 1.8 μm and short polar filament, turned into four coils. The obtained data show that this species differs from all previously described Myxobolus spp. with equal polar capsules. Comparative study of Myxobolus spp. recorded in worldwide mullets indicates a close relationship with M. adeli n. sp. and Myxobolus improvisus Isjumova, 1964 registered in mullets. Probably, the last species includes representatives of some different species, infecting freshwater and marine hosts.

Parasite fauna of Golden Grey Mullet Liza aurata (Risso, 1810) collected from Lower Kızılırmak Delta in Samsun, Turkey

Abstract The mugilids are among the most cosmopolitan teleost fishes and they are widely distributed in fresh, brackish and coastal marine waters of the tropical and temperate regions of the world. Liza aurata is one of eight mugilid species survive in Turkish waters. Parasite fauna of the golden grey mullet Liza aurata (Risso, 1810) collected from Lower Kızılırmak Delta in Samsun, Turkey were investigated in the present study. Standard parasitological investigation methods were applied and standard indices of infection were calculated. A total of 10 parasite species were identified and they are; Trichodina puytoraci, Trichodina lepsii, Ligophorus mediterraneus, Ligophorus cephali, Microcotyle mugilis, Ascocotyle (Phagicola) longa, Haplosplanchnus pachysomus, Tylodelphys clavata, Neoechinorhyncus agilis and Ergasilus lizae. Overall infection prevalence was 100 % and both the mean intensity and abundance values were 190.09 ± 43.15 parasites per infected/examined fish. Ligophorus-group parasites were the most abundant (97.83 %) and Tylodelphys clavata was the least (4.35 %) among all parasite species identified. Water temperature (C), dissolved oxygen (mg/lt), salinity (ppt) and nitrate (mg/lt) values were also presented. According to results obtained in the present study, Ligophorus cephali, Ligophorus mediterraneus, Thylodelphys clavata and Ascocotyle (Phagicola) longa are new parasite records for L. aurata and Ligophorus mediterraneus, Ligophorus cephali and Ergasilus lizae are the new parasite records for Turkish parasite fauna of fish in Turkey.

Behavioral responses of juvenile golden gray mullet Liza aurata to changes in coastal temperatures and consequences for benthic food resources

Temperature is an important factor for fish. Yet, little is known about temperature effects on the feeding behavior of fish and the subsequent consequences of these behavioral changes on the spatial distribution of resources. We analyzed the differences in the feeding behavior of two size classes of juvenile Liza aurata at two water temperatures (i.e. 10°C and 20°C), using laboratory mesocosms. We also examined whether potential temperature-induced changes in feeding behavior of the smaller size of L. aurata would affect the spatial distribution of the microphytobenthos (MPB) biomass, an important resource in coastal systems.Both the number of feeding events and the swimming velocity during feeding were higher at 20°C than at 10°C, independent of the fish size. The time spent feeding did not vary between 10°C and 20°C, while the distance covered during feeding was significantly smaller at 20°C than at 10°C. Grazing did not affect the mean MPB biomass, but did increase its spatial variance at the smaller scale (i.e. a few centimeters) at 20°C.A high number of feeding events, a high swimming velocity during feeding and a small distance covered during feeding in 20°C-acclimated L. aurata most likely represented an adaptation to an increase in metabolism, as well as to the need to reduce the energy costs of feeding at 20°C. Results also indicated that changes in feeding behavior of the 20°C-acclimated L. aurata were responsible for the increase in small-scale spatial variability in the MPB biomass but not an overall significant effect on the MPB mean. We suggested that the enhanced spatial patchiness due to grazing by fish at 20°C might yield a local increase in the mean MPB biomass, probably increasing photosynthetic efficiency of cells and algal growth that counterbalance the negative effect of algal removal by fish.

New and rare coastal fishes in the Azores islands: occasional events or tropicalization process?

Seven coastal fish species are newly reported for the remote north Atlantic archipelago of the Azores: Mediterranean sand eel Gymnammodytes cicerelus, bar jack Caranx ruber, two-banded seabream Diplodus vulgaris, bastard grunt Pomadasys incisus, unicorn leatherjacket filefish Aluterus scriptus and longspined porcupinefish Diodon holacanthus. The occurrence is also confirmed for 19 species that had been hitherto cited occasionally for the region, totalling a list of two elasmobranchs and 23 teleosts. Diplodus vulgaris, which appears to have recently colonized the islands, as well as roughtail stingray Dasyatis centroura and golden grey mullet Liza aurata, re-cited based on new records, are frequent or common coastal species in the Azores. The remaining 22 species, exceptional or rare in the region, are of tropical or subtropical affinity and find their northernmost distribution limit within the central and north-east Atlantic Ocean precisely in the Azores. This biogeographical pattern contrasts with that of the Azorean coastal fish community and suggests a tropicalization process in the region in line with previous findings of similar patterns across the north-east Atlantic Ocean and the Mediterranean Sea. These novel data from the most isolated archipelago of the North Atlantic Ocean, located in a biogeographic boundary area where colonization opportunities are reduced, reinforce the need for long-term monitoring programmes of coastal fish communities and, in particular, of indicator species groups to improve understanding of the effects of climate change on marine communities.

Reproductive biology of the Golden grey mullet Liza aurata, in the Gulf of Gabes (central Mediterranean, Tunisia) in the Gulf of Gabes (central Mediterranean, Tunisia)

In spite of its high commercial value, very few information are available on the biological feature of the Golden grey mullet in Tunisian waters (central Mediterranean). These data would be of great help in identifying the current stock state. In this study, Gonado Somatic Index (GSI), Hepato Somatic Index (HSI), condition factor (K), Length at first sexual maturity TL50 was calculated and the fecundity was estimated using the volumetric method. The Gonado Somatic Index (GSI) indicated that the spawning season of the Golden grey mullet extends from October to December. The monthly variation of Hepato-Somatic Index (HSI) indicates that L. aurata saves lipid reserves in liver. The species is sexually mature at 23.73, 23.84 and 23.79 cm TL respectively for female, male and combined sexes. In the present study the sex-ratio was unbalanced, with females dominating among large size individuals (TL > 24 cm). Absolute fecundity with a mean value of 286564 varied from a minimum of 210400 eggs for age 4 and a maximum of 533600 for age 7+.

Trophic shift in young‐of‐the‐year Mugilidae during salt‐marsh colonization

This study investigated the trophic shift of young-of-the-year (YOY) thinlip grey mullet Liza ramada and golden grey mullet Liza aurata during their recruitment in a salt marsh located on the European Atlantic Ocean coast. Stable-isotope signatures (δ(13) C and δ(15) N) of the fishes followed a pattern, having enrichments in (13) C and (15) N with increasing fork length (LF ): δ(13) C in fishes < 30 mm ranged from -19.5 to -15.0‰, whereas in fishes > 30 mm δ(13) C ranged from -15.8 to -12.7‰, closer to the level in salt-marsh food resources. Large differences between the δ(15) N values of mugilids and those of food sources (6·0‰ on average) showed that YOY are secondary consumers, similar to older individuals, when feeding in the salt marsh. YOY mugilids shift from browsing on pelagic prey to grazing on benthic resources from the salt marsh before reaching 30 mm LF. The results highlight the role of European salt marshes as nurseries for juvenile mugilids.

Polychlorinated biphenyl accumulation and hepatic EROD activity in golden grey mullet Liza aurata from Tunis Bay, southern Mediterranean

Liza aurata was used as a bioindicator species to monitor contamination by organic xenobiotics of estuarine water at the outlet of Khélij channel [canal], Tunisia, from November 2002 to December 2003. Polychlorinated biphenyl (PCB) concentrations, including coplanar congeners, were measured in mullet muscle tissue. Mean PCB concentrations ranged between 77 and 180 ng g−1 wet weight. The PCB profiles were dominated by hexachlorobiphenyl congeners accounting for 25–52% of the total profiles. Total 2,3,7,8-tetrachlorodibenzo-p-dioxin toxic equivalents of coplanar PCBs, including mono- and non-ortho congeners, was 4 pg g−1 wet weight in December 2003 vs 82 pg g−1 wet weight in April 2003. Biological effects in mullet were evaluated by measuring ethoxyresorufin-o-deethylase (EROD) activity in fish liver. EROD activity was significantly elevated, compared to baseline values in control fish (43 ± 23 pmol min−1 mg−1 protein). The highest enzymatic activity of 1 202 ± 813 pmol min−1 mg−1 protein was recorded in July 2003.

The effect of progressive hypoxia on spontaneous activity in single and shoaling golden grey mulletLiza aurata

The hypothesis of a differential effect of hypoxia on activity in shoaling v. solitary fish was tested in golden grey mullet Liza aurata. In both solitary and shoaling fish, (1) swimming activity increased significantly at <or=60% air saturation compared with normoxia, (2) aquatic surface respiration increased significantly below 15% air saturation and (3) a significant increase in ventilation frequency was observed between 40 and 10% air saturation. Swimming activity was higher in shoaling than in solitary fish, possibly due to social interactions in shoaling fish. Despite showing a higher swimming activity, shoaling individuals showed similar ventilation frequency to the less active solitary fish. This suggests that shoaling exerts a calming effect on L. aurata, probably related to increased safety while in numbers. In addition, shoaling fish spent a higher proportion of time performing aquatic surface respiration at 15% air saturation (i.e. the highest oxygen level at which aquatic surface respiration was observed) than solitary fish, possibly because of (1) synchronization of aquatic surface respiration in shoaling fish and (2) lower risk of predation perceived by shoaling fish.

Fast start performance in golden grey mullet Liza aurata exposed to sub-lethal concentrations of dispersed oil

Fast start performance in golden grey mullet Liza aurata exposed to sub-lethal concentrations of dispersed oil

The effect of hypoxia on locomotor performance and behaviour during escape in Liza aurata

Escape performance was investigated in the golden grey mullet Liza aurata exposed to various levels of oxygen: &gt;85 (i.e. normoxia), 50, 20 and 10 % air saturation. Since the golden grey mullet performed aquatic surface respiration when air saturation approached 15–10 %, escape performance was tested at 10 % air saturation with and without access to the surface (10 % S and 10 % C, respectively). Various locomotor and behavioural variables were measured, such as cumulative distance, maximum swimming speed, acceleration, responsiveness (per cent of responding fish), response latency and directionality. Golden grey mullet showed a decrease in responsiveness when the oxygen level was reduced to 10 % air saturation, whether the surface access was obstructed or not. Hypoxia did not have any effect on the response latency. Cumulative distance and maximum swimming speed over a fixed time were significantly different between normoxic conditions and 10 % C, while no differences were found in maximum acceleration. While the fish's ‘C‐bend’ was mainly directed away from the stimulus in normoxia, the proportion of away and towards ‘C‐bend’ was random when the oxygen was ≤20 % air saturation. This suggested an impairment of the left‐right discrimination at the initiation of the fast start. Hypoxia affected golden grey mullet escape performance mainly through an impairment of responsiveness and directionality, while locomotor performance was affected only in severe hypoxia when the surface was obstructed. The study showed that, in addition to forcing the fish to the surface as shown by previous studies, hypoxia may also reduce fish elusiveness facing a predator by directly impairing its escape performance.

A study on the scales and age estimation of the grey golden mullet, Liza aurata (Risso, 1810), in the lagoon of Messolonghi (W. Greece)

Summary A detailed study was made of the scales on the golden grey mullet Liza aurata in the lagoon of Messolonghi (W. Greece), in order to examine the suitability of scales for ageing. From a total of 1048 specimens of 9–59 cm total length (TL), the estimated ages ranged from 0+ to 8+ years, with only females at ages 7+ and 8+. The scale reading was reliable, the annuli recognizable and each annulus radius easily measured. There was a great overlapping in the annulus radius between the ages 1+ and 4+, indicative of extended spawning time and differences in growth of yearly recruits. The scale radius (Rmax) was strongly related with TL by the pooled equation: TL = 1.5501Rmax0.77, with no significant differences between the sexes. From examination of the monthly variation in the distance of the outermost annulus from the scale margin, it was determined that the annulus is formed in February. No annuli were detected in fish of less than 20 cm TL.

First record of Acanthocephala in marine copepods

Abstract Late cystacanth stages were discovered in the haemocoel of the marine benthic harpacticoid Halectinosoma herdmani (T. & A. Scott, 1896) (Copepoda: Ectinosomatidae) collected off La Rochelle, France. This represents the first record of Acanthocephala infesting marine copepods. On the basis of the hook formula on the proboscis and the spine pattern on the trunk, the parasites were identified as juveniles of Acanthogyrus (Acanthosentis) lizae Orecchia, Paggi & Radujkovic, 1988 (Eoacanthocephala: Gyracanthocephala: Quadrigyridae) which utilizes the golden grey mullet Liza aurata (Risso, 1810) as the definitive host. The literature on acanthocephalans utilizing copepods as intermediate hosts is reviewed and some morphological details of both the cystacanth and host copepod are presented using differential interference contrast and scanning electron microscopy. Halectinosoma porosum Wells, 1967 from Inhaca Island (Mozambique) is formally transferred to Ectinosoma Boeck, 1865 as E. porosum (Wells, 1967)...