Non-commercial invertebrate discards in an experimental trammel net fishery

Non-commercial invertebrate discards in an experimental trammel net fishery were studied in relation to selectivity of the gear, depth, soak time and season. Forty experimental fishing trials were carried out over a 1-year period with six combinations of small mesh (100, 120 and 140 mm) inner and large mesh (600 and 800 mm) outer panels. On average, 43.8 +/- 12.2 (SD) (individuals 1000 m(-1) of net) of non-commercial invertebrates were discarded, accounting for 48% and 65% of the total catch and total discards by numbers, respectively. Within non-commercial invertebrates discards, the six most abundant species by number were Phallusia mammillata (Cuvier) (27.5%), Cymbium olla (L.) (13.0%), Sphaerechinus granularis (Lamarck) (11.3%), Paracentrotus lividus (Lamarck) (10.9%), Astropartus mediterraneus (Risso) (8.2%) and Astropecten aranciacus (L.) (8.1%); Echinoderms (43.1%) particularly important. The highest and lowest discard ratios were found in autumn and winter, respectively. Discards generally decreased with depth, varied considerably in relation to soak time and were not related to mesh size combinations. Trammel nets seem to be the most important gear in terms of ecological impacts on benthic invertebrates compared with other coastal fishing gears and at the depths studied (15-60 m)

Comparative study on volatile compounds, fatty acids, squalene and quality parameters from whole fruit, pulp and seed oils of two tunisian olive cultivars using chemometrics

The oils of olive fruits, pulps and seeds of two main Tunisian cultivars of olive trees (Chemlali and Oueslati) were extracted at two different indices of maturity. The free acidity, peroxide value, spectrophotometric indices, chlorophyll content, squalene, fatty acids, aroma, and sensory profiles of oils were analyzed. Fruits and pulp oils had similar fatty acids compositions. While, seed oils have fatty acid profile that are different from both varieties. For the first time in this work, squalene content in the fruit, pulp, and seeds oils were measured by gas chromatography and it decreased during maturation. Its concentration in the seed oils were lower than those found in fruit and pulp oils. The volatile profiles of twelve Tunisian olive oils obtained from different parts of fruits were established by solid phase micro-extraction (SPME) coupled with gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). Sixty-six compounds were identified and characterized, representing 92.4 and 97.6% of the total volatiles. Principal component analysis showed that olive oil quality is strongly affected by olive cultivar, maturity index and the different olive parts

Age and growth, mortality, reproduction and relative yield per recruit of the bogue, Boops boops Linne, 1758 (Sparidae), from the Algarve (south of Portugal) longline fishery

Samples of Boops boops ranging from 7.4 to 30.5 cm were obtained mainly by longline, supplemented by beach seining in the Ria Formosa lagoon, and by market sampling in the Algarve (southern Portugal). The macroscopic analyses of the gonads and the gonad somatic index showed that the south coast of Portugal B. boops spawn mainly from late winter to spring, between February and May. The length at first maturity was similar for males and females and the value for both sexes combined was estimated to be 15.22 cm, corresponding to an age range of 1-3. Age was determined by reading growth bands on otoliths. Age determination was validated by marginal increment analysis. The estimated parameters were L-infinity = 28.06, K = 0.22 and t(0) = -1.42. Mortality rates were calculated for fish captured with longlines, and the estimated parameters were M = 0.33, Z = 1.04 and F = 0.71. Relative yield per recruit analysis and sensitivity analysis showed that the resource is moderately exploited. From the perspective of sustainability, these results provide support for the use of longlines as a gear that is among the least harmful for species such as the bogue

Seasonal inter-calibration between acoustic and multi-mesh gillnets sampling for fish biomass assessment in reservoirs

This paper presents the results of an inter‐calibration between acoustic and gillnets sampling in two North African reservoirs according to seasons. Gillnets with multi‐mesh were designed for sampling fish in lakes while acoustic surveys were performed with a split beam Simrad EK60 echosounder. Sampling events were carried out during summer (September 2015), autumn (December 2015), winter (March 2016) and spring (June 2016) in two Tunisian reservoirs (Kasseb and Siliana) with different depths and shapes. Gillnet catches showed a high proportion of barbell whatever the seasons in Kasseb Reservoir, while at Siliana Reservoir, significant seasonal changes in relative abundances have been evidenced. The highest fish biomass of the entire water column was observed in winter daytime (103 kg/ha) in Kasseb Reservoir and in summer daytime (283 kg/ha) in Siliana Reservoir. Average biomass observed in autumn (December) for the two reservoirs were lower than the other seasons. During spring, density daytime values in Kasseb were higher than during nighttime while it was the opposite in summer and autumn. Fish densities detected in Kasseb Reservoir in vertical beaming was higher than those detected in horizontal beaming (p < .05). The longitudinal distribution of fish in the reservoirs showed that there is no clear trend in fish densities according to strata. High numbers of fish were detected in deep strata and big fish were located in the surface water near the dam of Kasseb Reservoir. A significant linear correlation was showed between acoustic density/ NPUE and acoustic biomass/BPUE but the perfect correlation with the 1:1 fit was showed only between acoustic biomass/BPUE.This is the pre-peer reviewed version of the following article: [Laouar H, Djemali I. Seasonal inter‐calibration between acoustic and multi‐mesh gillnets sampling for fish biomass assessment in reservoirs. J Appl. Ichthyol. 2018.:00, pp.1-11 IN PRESS], which has been published in final form at [https://doi.org/10.1111/jai.13696]. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.In Pres