Accounting for environmental and fishery management factors when standardizing CPUE data from a scientific survey: A case study for Nephrops norvegicus in the Pomo Pits area (Central Adriatic Sea)

Abstract

Abundance and distribution of commercial marine resources are influenced by environmental variables, which together with fishery patterns may also influence their catchability. However, Catch Per Unit Effort (CPUE) can be standardized in order to remove most of the variability not directly attributable to fish abundance. In the present study, Generalized Additive Models (GAMs) were used to investigate the effect of some environmental and fishery covariates on the spatial distribution and abundance of the Norway lobster Nephrops norvegicus within the Pomo/Jabuka Pits (Central Adriatic Sea) and to include those that resulted significant in a standardization process. N. norvegicus is a commercially important demersal crustacean, altering its catchability over the 24-h cycle and seasons according to its burrowing behavior. A historically exploited fishing ground for this species, since 2015 subject to specific fisheries management measures, is represented by the meso-Adriatic depressions, which are also characterized by particular oceanographic conditions. Both the species behaviour and the features of this study area influence the dynamics of the population offering a challenging case study for a standardization modelling approach. Environmental and catch data were obtained during scientific trawl surveys properly designed to catch N. norvegicus, thus improving the quality of the model input data. Standardization of CPUE from 2 surveys from 2012 to 2019 was conducted building two GAMs for both biomass and density indices. Bathymetry, fishing pressure, dissolved oxygen and salinity proved to be significant drivers influencing catch distribution. After cross validations, the tuned models were then used to predict new indices for the study area and the two survey series by means of informed spatial grids, composed by constant surface cells, to each of which are associated average values of environmental parameters and specific levels of fishing pressure, depending on the management measures in place. The predictions can be used to better describe the structure and the spatio-temporal distribution of the population providing valuable information to evaluate the status of such an important marine resource.

Advancing fishery-independent stock assessments for the Norway lobster (Nephrops norvegicus) with new monitoring technologies

“…comm. ;GFCM, 2022) taking into account, in addition to traditional data: the available UWTV data (Martinelli et al, 2013;Martinelli et al, 2022), new assumptions on the availability of the species to trawl fishery (Aguzzi et al, 2021), the presence in the area of various subpopulations with limited connectivity (Melaku Canu et al, 2021) and different biological characteristics (Angelini et al, 2020), the spatial origin of the commercial catches (Russo et al, 2018) and standardized trawl data from a survey specifically targeting N. norvegicus and not covered by DCF (Chiarini et al, 2022).…”

Dataset of Depth/Temperature profiles obtained in the period 2012–2020 using commercial fishing vessels of the AdriFOOS fleet in the Adriatic Sea (Mediterranean Sea)

“…temperature, salinity, oxygen and chlorophyll) and their changes in time In the near future, the refinement of the AdriFOOS catch and bottom parameters datasets and their inclusion in species abundance and distribution models (e.g. Carpi et al, 2015;Chiarini et al, 2022) will allow increasing the knowledge of fish spatial movements, influence of environmental drivers and climate change on their distribution and abundance and status of exploitation of a resource; this is of utmost relevance in the framework of an ecosystem approach to fisheries management.…”

“…Therefore, this methodology allows to acquire data profiles along the water column and measurements at the depth at which the fishing operation takes place, which often occurs close to the sea bottom. Recently, a dataset containing 14810 depth (pressure)/temperature profiles has been made accessible (Penna et al, 2020); this was generated in the period 2012-2020 by 10 vessels belonging to the AdriFOOS fleet and 1 FOOS installed on board the CNR R/V Dallaporta (while carrying out experimental trawl surveys in the central Adriatic Sea; Chiarini et al, 2022). This huge amount of data could be very useful to improve the knowledge about Adriatic Sea mesoscale oceanographic processes and detect possible shifts due to climate change; in addition this could be used to feed operational model though data assimilation and reanalysis as already trialled in the framework of the JERICO -NEXT Project (Mourre et al, 2019).…”

Identifying priority areas for spatial management of mixed fisheries using ensemble of multi‐species distribution models

“…Additional information on sediment type (grain size) was considered for common sole, cuttlefish, and mantis shrimp due to the availability of data connected to TBB surveys. Conversely, although important for other OTB species such as Norway lobster, grain size was not considered due to lack of available data (Chiarini et al., 2022).…”