Manage or restrict harvesting of species on subtidal artificial structures

How is the evidence assessed?
  • Effectiveness
    not assessed
  • Certainty
    not assessed
  • Harms
    not assessed

Study locations

Key messages

  • Three studies examined the effects of managing or restricting harvesting of species on subtidal artificial structures on the biodiversity of those structures or on human behaviour likely to influence the biodiversity of those structures. The studies were on open coastlines in Italy.

COMMUNITY RESPONSE (1 STUDY)

  • Fish community composition (1 study): One site comparison study in Italy found different fish community composition around subtidal artificial structures with and without harvesting restrictions. The structure with harvesting restrictions supported species that were absent from unrestricted structures.
  • Fish richness/diversity (1 study): One site comparison study in Italy found higher fish species richness around a subtidal artificial structure with harvesting restrictions compared with unrestricted structures.

POPULATION RESPONSE (2 STUDIES)

  • Invertebrate abundance (1 study): One site comparison study in Italy found similar sea urchin abundances around subtidal artificial structures with and without harvesting restrictions.
  • Fish abundance (2 studies): One of two site comparison studies in Italy found similar total fish abundance around subtidal artificial structures with and without harvesting restrictions, but that abundances varied depending on the species and the survey date. One study found higher seabream abundances around the structure with harvesting restrictions.

BEHAVIOUR (1 STUDY)

  • Human behaviour change (1 study): One replicated, randomized study in Italy reported that legally restricting human access on subidal artificial structures did not prevent people from harvesting invertebrates and fishes on and around structures.

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

  1. A replicated, randomized study in 2001–2002 on subtidal breakwaters and groynes in five sites on open coastline in the Adriatic Sea, Italy (Airoldi et al. 2005) reported that making access to the breakwaters illegal did not prevent people from harvesting invertebrates and fishes on and around them. At four sites, an average of 0–2 harvesters/2-hour survey were recorded on breakwaters, despite access being illegal. At one site where breakwaters (access illegal) and groynes (access legal) were studied simultaneously, an average of 0–5 harvesters/2-hour survey were recorded. At this site >70% of observations were on groynes, but harvesting also occurred on breakwaters (details not reported). Harvesting species on breakwaters was restricted by making access illegal, but with no apparent enforcement (timing and other details not reported). The number of people harvesting invertebrates and fishes on breakwaters at each of five sites was counted during 2-hour surveys on 152 randomly-selected days between November 2001 and November 2002. Observations at one of the sites included harvesting on groynes, to which access was legal.

    Study and other actions tested
  2. A site comparison study in 2002–2003 on three subtidal breakwaters on open coastline in the Adriatic Sea, Italy (Guidetti, Bussotti & Boero 2005; same experimental set-up as Guidetti et al. 2005) found higher abundances of white seabream Diplodus sargus, two-banded seabream Diplodus vulgaris and gilt-head seabream Sparus aurata, but similar abundance of sea urchins Paracentrotus lividus around a breakwater with restricted harvesting, compared with two unrestricted breakwaters. Sixteen years after harvesting restrictions were introduced, abundance was higher around the breakwater with restrictions than those without for white seabream in two of four surveys (restricted: 5–8 individuals/125m2; unrestricted: 0–2/125m2) and for two-banded seabream in three surveys (restricted: 2–46/125m2; unrestricted: 0–14/125m2). In the remaining surveys, abundances were similar around restricted (white: 3–10/125m2; two-banded: 4/125m2) and unrestricted breakwaters (white: 0–8/125m2; two-banded: 1–3/125m2). Gilt-head seabream were present only at the restricted breakwater in three of the surveys (1–2/125m2) and was more abundant in the fourth (restricted: 2/125m2; unrestricted: <1/125m2). Urchin abundance was similar around restricted and unrestricted breakwaters (both 2–11/20m2). Harvesting species on and around a boulder breakwater was restricted by creating a marine protected area in 1986, making fishing illegal with successful enforcement. Fishes and sea urchins were counted during four surveys at 4–7 m depth in 2002–2003 around the breakwater with restricted harvesting and around two nearby breakwaters with no restrictions.

    Study and other actions tested
  3. A site comparison study in 2002–2003 on three subtidal breakwaters on open coastline in the Adriatic Sea, Italy (Guidetti et al. 2005; same experimental set-up as Guidetti, Bussotti & Boero 2005) found higher fish species richness and different fish community composition around a breakwater with restricted harvesting, compared with two unrestricted breakwaters, while fish abundances varied depending on the species and survey date. Sixteen years after harvesting restrictions were introduced, the fish species richness was higher around the breakwater with restrictions (24–27 species/breakwater) than those without (13–22/breakwater) and the fish community composition differed in seven of eight comparisons (data reported as statistical model results). Total fish abundance was higher around the restricted breakwater in only one of four surveys (152 vs 63–66 individuals/survey) but was similar in three (319–554 vs 192–841/survey). However, the individual abundances of eight of 12 fish species were higher around the restricted breakwater during two or more surveys (see paper for full results). Three fish species recorded around the restricted breakwater were absent from unrestricted breakwaters. Harvesting species on and around a boulder breakwater was restricted by creating a marine protected area in 1986, making fishing illegal with successful enforcement. Fishes were counted during four surveys at 4–7 m depth in 2002–2003 around the breakwater with restricted harvesting and around two nearby breakwaters with no restrictions.

    Study and other actions tested
Please cite as:

Evans, A.J., Moore, P.J., Firth, L.B., Smith, R.K., and Sutherland, W.J. (2021) Enhancing the Biodiversity of Marine Artificial Structures: Global Evidence for the Effects of Interventions. Conservation Evidence Series Synopses. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

All the journals searched for all synopses

Biodiversity of Marine Artificial Structures

This Action forms part of the Action Synopsis:

Biodiversity of Marine Artificial Structures
Biodiversity of Marine Artificial Structures

Biodiversity of Marine Artificial Structures - Published 2021

Enhancing biodiversity of marine artificial structures synopsis

What Works 2021 cover

What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

More about What Works in Conservation

Download free PDF or purchase
The Conservation Evidence Journal

The Conservation Evidence Journal

An online, free to publish in, open-access journal publishing results from research and projects that test the effectiveness of conservation actions.

Read the latest volume: Volume 19

Go to the CE Journal

Discover more on our blog

Our blog contains the latest news and updates from the Conservation Evidence team, the Conservation Evidence Journal, and our global partners in evidence-based conservation.


Who uses Conservation Evidence?

Meet some of the evidence champions

Endangered Landscape Programme Red List Champion - Arc Kent Wildlife Trust The Rufford Foundation Save the Frogs - Ghana Bern wood Supporting Conservation Leaders National Biodiversity Network Sustainability Dashboard Frog Life The international journey of Conservation - Oryx British trust for ornithology Cool Farm Alliance UNEP AWFA Butterfly Conservation People trust for endangered species Vincet Wildlife Trust