Towards Non-Invasive Methods to Assess Population Structure and Biomass in Vulnerable Sea Pen Fields

Abstract

Colonies of the endangered red sea pen Pennatula rubra (Cnidaria: Pennatulacea) sampled by trawling in the northwestern Mediterranean Sea were analyzed. Biometric parameters, such as total length, peduncle length, number of polyp leaves, fresh weight, and dry weight, were measured and related to each other by means of regression analysis. Ad hoc models for future inferencing of colonies size and biomass through visual techniques were individuated in order to allow a non-invasive study of the population structure and dynamics of P. rubra.

Mesophotic and Deep-Sea Vulnerable Coral Habitats of the Mediterranean Sea: Overview and Conservation Perspectives

“…Sea pens (subclass Octocorallia, order Pennatulacea) live on soft bottoms, from shallow to deep waters, and they can form dense aggregations known as sea pen fields which increase the complexity of an otherwise flat and monotonous seabed [76,77]. Pennatula rubra (Ellis, 1761) (Figure 1f), Pteroeides spinosum (Ellis, 1764) and Veretillum cynomorium (Pallas, 1766) are typical field-forming species of the continental shelf, being occasionally present form the euphotic zone but forming true fields only in the mesophotic [24,[78][79][80]. Pennatula phosphorea Linnaeus, 1758 and Virgularia mirabilis (Müller, 1776) can occur from mesophotic to deep seabed, often in mixed aggregation with other soft-bottom anthozoans, while Funiculina quadrangularis (Pallas, 1766) and Kophobelemnon stelliferum (Müller, 1776) represent deep-sea pennatulaceans able to form dense fields on the aphotic muddy bottoms [31,81,82].…”

Cold-water corals and deep-sea sponges by-catch mitigation: Dealing with groundfish survey data in the management of the northwest Atlantic Ocean high seas fisheries

“…Particularly, visual methodologies are more accurate and efficient for studying abundance of benthic populations in small areas (e.g. seapens), but they are often not appropriate for studying their biomass and size structure [59,61]. However, NEREIDA programme made substantive progress in the use of non-invasive sampling techniques to monitor VMEs in the NAFO Regulatory Area.…”

“…Chimenti et al [59,61] suggested that trawl data is still necessary to identify areas of high concentrations of cold-water corals (e.g. sea pen fields) at large scale, but ROV images could be used afterwards to monitor these concentrations in a non invasive way, consistent with the precautionary approach.…”

“…ROV) to map the entire distribution of VMEs is not feasible [65]. Additional research will be needed about the calibration and validation [61,66] of new non-invasive surveys with traditional bottom trawl surveys to enable a future combined series of data for monitoring purposes [29,63]. The work undertaken during the NEREIDA project provided good baseline data for in situ observations [67].…”

Mesophotic rocks dominated by Diazona violacea: a Mediterranean codified habitat

“…Although not precise and not always easy to asses, the number of zooids can represent a valuable proxy for population structure in D. violacea considering that ascidians, like many other marine invertebrates (e.g. Chimienti et al 2018Chimienti et al , 2019b, can show a highly variable contraction state that makes size measurements ineffective. The asexual reproduction of D. violacea concerns solely the establishment and growth of the colony by increasing the number of zooids each years, but it does not generate further colonies.…”