scholarly journals Assessing interactions between dolphins and small pelagic fish on branchline to design a depredation mitigation device in pelagic longline fisheries

2015 ◽  
Vol 72 (5) ◽  
pp. 1682-1690 ◽  
Author(s):  
Njaratiana Rabearisoa ◽  
Pascal Bach ◽  
Francis Marsac
Keyword(s):  
Bottlenose Dolphins ◽  
Pelagic Fish ◽  
Deterrent Effect ◽  
Small Scale ◽  
Small Pelagic Fish ◽  
Video Footage ◽  
Spinner Dolphins ◽  
Pilot Whales ◽  
Longline Fisheries ◽  
Pelagic Longline

Abstract Depredation by false killer whales (Pseudorca crassidens) and short-finned pilot whales (Globicephala macrorhynchus) in pelagic longlining is an issue leading to negative impacts on the economics of the fishery and on odontocetes themselves. We investigated the efficacy of a new depredation mitigation device called “DEPRED” in the interaction between bottlenose dolphins (Tursiops aduncus), spinner dolphins (Stenella longirostris), and small pelagic fish (SPF) attached to branchlines to simulate caught fish. We suggest implications for DEPRED efficacy with larger toothed whales interacting with pelagic longline capture in the open ocean. The design of the device uses streamers to both deter cetaceans and protect fish from predation. In controlled experiments, we tested its efficacy by observing changes in the dolphin's behaviour brought on by the presence or absence of the device on branchlines. First, dolphin–SPF interactions were observed at the small scale using video footage recorded with an underwater camcorder. Second, the efficacy of the device was quantified from interactions between dolphins and 80 branchlines deployed on a longline 500 m long baited with SPF. One half of the SPF on successive branchlines was protected by DEPRED and the other half was not. A total of 707 branchlines were set when dolphins interacted with SPF, and among them, 355 were equipped with DEPRED. Encouraging results were obtained: over the short term, the number of damaged unprotected SPF was on average more than twice the number of protected ones. Nevertheless, habituation behaviour was observed for a resident group of T. aduncus in the experimental area. The relation between the deterrent effect of the device and constraints related to the design of such a device to be used at a commercial operational level are discussed.

scholarly journals Characteristics of the Croatian anchovy purse seiner fleet

2019 ◽  
Vol 60 (1) ◽  
pp. 79-85
Author(s):  
Alen Soldo ◽  
Neven Bosnić ◽  
Vice Mihanović
Keyword(s):  
Precise Determination ◽  
Pelagic Fish ◽  
Purse Seine ◽  
Small Scale ◽  
Small Pelagic Fish ◽  
Fishing Fleet ◽  
Fishing Vessels ◽  
Fishing Capacity

Croatia has a fishing fleet of 7559 vessels. Of these, small-scale coastal fishing boats, less than 12 meters in length, makes up 95,7% of the fleet. However, the largest percentage of catches, more than 94%, is made by purse-seiners that are representing only 3% of total fishing vessels. These vessels target small pelagic fish, predominately sardine and anchovy. This paper describes all the technical characteristics of the Croatian purse seiner fleet, based on 113 purse seine vessels registe-red in 6 Croatian ports and targeting anchovy in order to allow a precise determination of that fleet fishing capacity and subsequent management of the fleet in a responsible and sustainable manner. Comparison of different technical characteristics showed that the length of a vessel corresponds to the amount of the catch as well as to size of the fish. Hence, results confirm superiority of sonar, as a fish-finding device, over sounder in detecting fish shoals, which is prerequisite for purse seine fishing.

scholarly journals Shark depredation rates in pelagic longline fisheries: a case study from the Northwest Atlantic

2009 ◽  
Vol 66 (4) ◽  
pp. 708-719 ◽  
Author(s):  
M. Aaron MacNeil ◽  
John K. Carlson ◽  
Lawrence R. Beerkircher
Keyword(s):  
Large Scale ◽  
Linear Models ◽  
Negative Binomial ◽  
Small Scale ◽  
Northwest Atlantic ◽  
Novel Technologies ◽  
Catch Composition ◽  
Longline Fisheries ◽  
Pelagic Longline

Abstract MacNeil, M. A., Carlson, J. K., and Beerkircher, L. R. 2009. Shark depredation rates in pelagic longline fisheries: a case study from the Northwest Atlantic. – ICES Journal of Marine Science, 66: 708–719. A suite of modelling approaches was employed to analyse shark depredation rates from the US Atlantic pelagic longline fishery. As depredation events are relatively rare, there are a large number of zeroes in pelagic longline data and conventional generalized linear models (GLMs) may be ineffective as tools for statistical inference. GLMs (Poisson and negative binomial), two-part (delta-lognormal and truncated negative binomial, T-NB), and mixture models (zero-inflated Poisson, ZIP, and zero-inflated negative binomial, ZINB) were used to understand the factors that contributed most to the occurrence of depredation events that included a small proportion of whale damage. Of the six distribution forms used, only the ZIP and T-NB models performed adequately in describing depredation data, and the T-NB and ZINB models outperformed the ZIP models in bootstrap cross-validation estimates of prediction error. Candidate T-NB and ZINB model results showed that encounter probabilities were more strongly related to large-scale covariates (space, season) and that depredation counts were correlated with small-scale characteristics of the fishery (temperature, catch composition). Moreover, there was little evidence of historical trends in depredation rates. The results show that the factors contributing to most depredation events are those already controlled by ships' captains and, beyond novel technologies to repel sharks, there may be little more to do to reduce depredation loss in the fishery within current economic and operational constraints.

The box-balance model: a new tool to assess fish larval survival, applied to field data on two small pelagic fish

2020 ◽  
Vol 650 ◽  
pp. 289-308 ◽  
Author(s):  
V Raya ◽  
J Salat ◽  
A Sabatés
Keyword(s):  
Field Data ◽  
Fish Larvae ◽  
Larval Growth ◽  
Warming Trend ◽  
Mortality Rates ◽  
Larval Survival ◽  
Pelagic Fish ◽  
Balance Model ◽  
Small Pelagic Fish ◽  
Mesoscale Structures

This work develops a new method, the box-balance model (BBM), to assess the role of hydrodynamic structures in the survival of fish larvae. The BBM was applied in the northwest Mediterranean to field data, on 2 small pelagic fish species whose larvae coexist in summer: Engraulis encrasicolus, a dominant species, and Sardinella aurita, which is expanding northwards in relation to sea warming. The BBM allows one to quantify the contribution of circulation, with significant mesoscale activity, to the survival of fish larvae, clearly separating the effect of transport from biological factors. It is based on comparing the larval abundances at age found in local target areas, associated with the mesoscale structures (boxes), to those predicted by the overall mortality rate of the population in the region. The application of the BBM reveals that dispersion/retention by hydrodynamic structures favours the survival of E. encrasicolus larvae. In addition, since larval growth and mortality rates of the species are required parameters for application of the BBM, we present their estimates for S. aurita in the region for the first time. Although growth and mortality rates found for S. aurita are both higher than for E. encrasicolus, their combined effect confers a lower survival to S. aurita larvae. Thus, although the warming trend in the region would contribute to the expansion of the fast-growing species S. aurita, we can confirm that E. encrasicolus is well established, with a better adapted survival strategy.

Small pelagic fish responses to fine-scale oceanographic conditions: implications for the endangered African penguin

2017 ◽  
Vol 569 ◽  
pp. 187-203 ◽  
Author(s):  
AM McInnes ◽  
PG Ryan ◽  
M Lacerda ◽  
J Deshayes ◽  
WS Goschen ◽  
...  
Keyword(s):  
Pelagic Fish ◽  
Fine Scale ◽  
Small Pelagic Fish ◽  
African Penguin ◽  
Oceanographic Conditions

PEMETAAN RANTAI NILAI IKAN PELAGIS KECIL DI KOTA AMBON

2018 ◽  
Vol 2 (1) ◽  
pp. 15-21
Author(s):  
Yolanda MTN Apituley ◽  
Dionisius Bawole ◽  
Imelda KE Savitri ◽  
Friesland Tuapettel
Keyword(s):  
Value Chain ◽  
Secondary Data ◽  
Pelagic Fish ◽  
Value Chain Analysis ◽  
Small Pelagic Fish ◽  
Fresh Fish ◽  
Chain Analysis ◽  
The Government ◽  
Market Distance ◽  
Role Of The Government

This research was taken in Ambon (Latuhalat and Laha) and in Central Maluku Regency (Waai) in May – July 2018. It was aimed at mapping the value chain of small pelagic fish in Ambon through: 1) mapping of product, financial and information flows and 2). analysis of percentage distribution of small pelagic fish caught. The data used in this study was primary and secondary data, and analyzed by using value chain analysis. The results show that small pelagic fish marketing chain in Ambon consisted of six models with five actors. Each chain is formed due to the conditions and situation of market, resulted by the influencing of catches of fishermen and traders' capital. The broker plays an important role in marketing small pelagic fish in the market and obtaining 10% of the fishermen's catch that can be distributed, both to retailers and cold storage. Fish caught by the fishermen is still fresh in general when arrives in the consumers, because the fishing area is not too far, the market distance with the production centers is also quite close and in general fishermen and traders have understood the importance of maintaining product quality. Even so, the role of the Government in providing marketing facilities and infrastructure is needed so that modern market conditions can be applied in marketing fresh fish in Ambon.

scholarly journals Determinants of lungworm specificity in five cetacean species in the western Mediterranean

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Rachel Pool ◽  
Clara Romero-Rubira ◽  
Juan Antonio Raga ◽  
Mercedes Fernández ◽  
Francisco Javier Aznar
Keyword(s):  
Bottlenose Dolphins ◽  
Parasite Burden ◽  
Western Mediterranean ◽  
Host Size ◽  
Cetacean Species ◽  
Stenella Coeruleoalba ◽  
Species Similarity ◽  
Pilot Whales ◽  
Common Dolphins ◽  
Prey Overlap

Abstract Background Current data about Pseudaliidae show contrasting patterns of host specificity between congeneric species. We investigated how both contact and compatibility between hosts and parasites contributed to the patterns of lungworm infection observed in a community of five species of cetaceans in the western Mediterranean. Methods The lungs of 119 striped dolphins Stenella coeruleoalba, 18 bottlenose dolphins Tursiops truncatus, 7 Risso’s dolphins Grampus griseus, 7 long-finned pilot whales Globicephala melas, and 6 common dolphins Delphinus delphis were analysed for lungworms. Parasites were identified by morphology and analysis of ITS2 sequences using both maximum likelihood and Bayesian inference methods. Body length was used as a proxy for lungworm species fitness in different hosts and compared with Kruskal-Wallis tests. Infection parameters were compared between cetacean species using Fisher’s exact tests and Kruskal-Wallis tests. Phylogenetic specificity was explored by collating the overall lungworm species prevalence values in hosts from previous surveys in various localities. To explore the relative importance of vertical and horizontal transmission, Spearman’s rank correlation was used to look for an association between host size and lungworm burden. A Mantel test was used to explore the association between lungworm species similarity and prey overlap using dietary data. Results Halocercus delphini had higher infection levels in striped dolphins and common dolphins; Stenurus ovatus had higher infection levels in bottlenose dolphins; and Stenurus globicephalae had higher infection levels in long-finned pilot whales. These results are congruent with findings on a global scale. Morphometric comparison showed that the larger nematodes were found in the same host species that had the highest parasite burden. Lungworms were found in neonatal striped dolphins and a Risso’s dolphin, and there was a weak but significant correlation between host size and parasite burden in striped dolphins and bottlenose dolphins. There was also a weak but significant association between prey overlap and lungworm species similarity. Conclusions Data indicate that phylogenetic specificity has an important role in governing host–parasite associations, as indicated by the higher infection levels and larger nematode size in certain hosts. However, diet can also influence infection patterns in these preferred hosts and contribute to less severe infections in other hosts.

Seabird bycatch vulnerability in pelagic longline fisheries based on modelling of a long-term dataset

2021 ◽  
pp. 1-16
Author(s):  
CAN ZHOU ◽  
NIGEL BROTHERS
Keyword(s):  
Capture Event ◽  
Retrieval Rate ◽  
Competitive Environments ◽  
Global Concern ◽  
Competitive Species ◽  
Spatio Temporal ◽  
Longline Fisheries ◽  
Pelagic Longline

Summary The incidental mortality of seabirds in fisheries remains a serious global concern. Obtaining unbiased and accurate estimates of bycatch rates is a priority for seabird bycatch mitigation and demographic research. For measuring the capture risk of seabird interactions in fisheries, the rate of carcass retrieval from hauled gear is commonly used. However, reliability can be limited by a lack of direct capture observations and the substantial pre-haul bycatch losses known to occur, meaning incidence of seabird bycatch is underestimated. To solve this problem, a new measure (bycatch vulnerability) that links an observed interaction directly to the underlying capture event is proposed to represent the capture risk of fishery interactions by seabirds. The new measure is not affected by subsequent bycatch loss. To illustrate how to estimate and analyse bycatch vulnerability, a case study based on a long-term dataset of seabird interactions and capture confirmation is provided. Bayesian modelling and hypothesis testing were conducted to identify important bycatch risk factors. Competition was found to play a central role in determining seabird bycatch vulnerability. More competitive environments were riskier for seabirds, and larger and thus more competitive species were more at risk than smaller sized and less competitive species. Species foraging behaviour also played a role. On the other hand, no additional effect of physical oceanic condition and spatio-temporal factors on bycatch vulnerability was detected. Bycatch vulnerability is recommended as a replacement for the commonly used bycatch rate or carcass retrieval rate to measure the capture risk of an interaction. Combined with a normalized contact rate, bycatch vulnerability offers an unbiased estimate of seabird bycatch rate in pelagic longline fisheries.

The effect of light attractor color in pelagic longline fisheries

2021 ◽  
Vol 235 ◽  
pp. 105822
Author(s):  
André S. Afonso ◽  
Bruno Mourato ◽  
Humberto Hazin ◽  
Fábio H.V. Hazin
Keyword(s):  
Longline Fisheries ◽  
Pelagic Longline ◽  
Effect Of Light

A new look on the morphometric characteristics of Congridae leptocephali from the southern Adriatic Sea

2021 ◽  
pp. 1-5
Author(s):  
M. Mandić ◽  
I. Leonori ◽  
A. De Felice ◽  
S. Gvozdenović ◽  
A. Pešić
Keyword(s):  
Fish Species ◽  
Adriatic Sea ◽  
Pelagic Fish ◽  
Morphometric Parameters ◽  
Morphological Features ◽  
Morphometric Characteristics ◽  
Small Pelagic Fish ◽  
Acoustic Surveys ◽  
Western Side ◽  
Conger Conger

Abstract Anguillid leptocephali of three Congridae species (Conger conger, Ariosoma balearicum and Gnathophis mistax) were caught as bycatch of pelagic trawls during acoustic surveys targeting small pelagic fish species in the southern Adriatic Sea, carried out under the framework of the Italian MEDIAS project (western side) and its extension in the ambit of the FAO AdriaMed project (eastern side). Results refer to the findings of Congridae leptocephali during surveys conducted in 2011, 2014, 2015 and 2016. A total of 25 specimens were caught and analysed (morphological features and pigmentation patterns). Leptocephali of Conger conger were found in the range of 8.4–13.1 cm total length (TL) (between 50 and 132 m depth), Ariosoma balearicum from 9.7–12.2 cm TL (between 50 and 128 m depth) and for Gnathophis mystax in the range from 6.4–11.7 cm TL (between 40 and 79 m depth). The results indicate that the southern Adriatic Pit could be the spawning area of these species in the Adriatic Sea. Present data represent a contribution to existing knowledge about the ecology of leptocephali from the Congridae family in the southern Adriatic Sea, and also indicate the existence of differences in morphometric parameters between different areas, that is, the possibility of the existence of new geographic lines within the genus Ariosoma in the Adriatic Sea.

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