(In)effectiveness of marine strict protection rotational zones


Scientific research around the world has shown the significant effectiveness of strict protection zones in preserving marine natural resources. Marine protected areas generally have larger quantities of fish and larger average lengths of fish, especially of economically important species, in comparison with unprotected areas or the situation before establishment of protection.

However, the inevitable consequence of strict protection in marine areas is the fishing ban, that is, the exclusion of recreational and commercial fishing. Over time, the spillover and recruitment effect brings benefits to fishermen in the surrounding area. This effect of protection takes a long time, so strict protection zones are often a source of conflicts in the beginning – due to the reduction of the fishing area, but also because it is difficult to accept that some areas become permanently inaccessible for fishing after the establishment of protection.

What are rotational zones?

One of the possible alternative strategies to the establishment of permanent strict protection zones is the establishment of rotational zones, i.e. alternating opening and closing of fishing areas. The aim is fish stocks restoration during the closing period so that fishing activity can be maintained during open periods. Although rotational closures appear to be beneficial for some sessile invertebrate species (e.g. scallops), there are only a few studies dealing with the long-term evaluation of the effectiveness of rotational fish stock management.

One of the rare areas that has documented the establishment and implementation of rotational zones for many years (and later the establishment of a permanent strict protection zone) is Waikiki-Diamond Head Shoreline Fishery Management Area in Hawaii. As a populated island state with a large number of commercial and recreational fishermen, Hawaii had a great need for the introduction of effective marine resource management strategies due to the increasing decline in catches and sizes of economically important species. Certain previous experiences indicated that the establishment of rotational zones is more acceptable for fishermen than those zones permanently closed for fishing.

Despite the initial plan of the Department of Water Resources to implement a rotational closure of the entire coastline of Oahu Island, after negotiations with the local community, it was decided to establish rotational zones in a smaller area. In 1978 the Waikiki-Diamond Head Shoreline Fishery Management Area was established (FMA) on the southeastern part of Oahu Island.

Comparison of models: rotational zones vs. permanent protection zones

The aim of the protection was restoration of fishing areas. Management was established on a four-year cycle: two years of area closure followed by two years of permitted fishing. During the first “open” year, only fishing hooks were allowed, while during the second year all types of fishing were allowed, except for night fishing with speargun and nets. Ten years after the establishment of rotational management, in 1987, part of the area was permanently protected as a strict protection zone, the Waikiki Marine Life Conservation District (MLCD). In other parts of an area, the rotation system was maintained, but changed to a two-year cycle (one year open and one year closed). During the open year, all types of fishing are allowed, except night fishing with spearguns and nets.

Since the situation in this area has been monitored for many years, there is enough data to enable the comparison of two different management models (rotational and permanent protection), i.e. related changes in the fish stock. Additionally, using data from Hawaii Comprehensive Study of Coral Reefs (2022), it was possible to compare fish populations in rotational and permanently closed zones with those in unprotected areas.

Within the rotational zone area (FMA), the biomass of economically important fish species tends to increase during the period of closure and to decrease during the open period. However, the decline during the open period was greater than the increase during the closing period and therefore the overall, net effect had a downward trend.

These results clearly show that the increase in biomass during the period of closure, in one to two years cycles, is not sufficient to offset the decline in biomass during the open fishing period. They are in line with numerous studies that show that the “accumulated” increase in biomass during several years of protection can be dissipated very quickly after the continuation of fishing. In this regard, the catch of fishermen is also slightly higher at the very beginning, after re-opening of the zone, but this situation only lasts for a few months. Documented trends within the Waikiki permanent strict protection zone (MLCD), show that there is a large increase in the biomass of economically important species in that zone compared to the rotation zones. In the period between 1990 and 1995, the invasive algae Gracilaria salicornia appeared only inside the permanent protection zone,  and covered large reef areas causing a drop in the total biomass. But still it was higher than within rotational zones. Despite the small total area and the negative impact of invasive algae, the permanent Waikiki strict protection zone has been proven to be more effective than rotational zones for the protection of fish stock. Therefore, their establishment has no alternative.

The highest growth occurs after a minimum of five years

The recorded significant decrease in the maximum size of target species caught within the rotation zones (FMA) indicates that the closure of a zone for up to two years is too short period for individuals to reach their maximum size. Namely, the highest biomass growth occurs after a minimum of five years due to the delayed effect of recruitment and the fact that the first few years after the closure, the fish stocks are dominated by very young individuals that do not contribute to the total biomass as much as the older ones (from two to four years). Although it is possible to increase the benefits of closed zones by extending the period of closure to more than two years, it should be emphasized that the full recovery of the area, in terms of its ecological functions, community structure and total biomass (especially large predatory species), requires more than 10 years.


Comparing the situation within the rotation zones with unprotected reefs, it was found that rotation zones don’t have a significantly higher biomass of fish species than those without an established protection regime. Even the attraction of intensive fishing immediately after the reopening of the area can be counterproductive and additionally affect the overall downward trend of such areas.

What do studies say about the effectiveness of protection zones in Croatia?

Research of the fishing stock within rotation zones in the Lastovsko otočje Nature Park, carried out by the Institute of Oceanography and Fisheries from Split in 2010, 2012 and 2013, showed similar results.

A good example in Croatia is Pomo pit, where, in order to protect shrimp and hake in its deepest part, a one-year ban on trawling was established in 2015. Over the years, the protection was extended, and even canceled at one point, and then finally in 2021, a decision was made to establish permanent protection of Pomo pit using the knowledge on the positive effects of protection from previous years. This area has become one of the best examples of good practice in the Mediterranean.

Share our story of strict protection zones in the Adriatic with others and support nature conservation – for a sea full of life.

Williams, I. D., Walsh, W. J., Miyasaka, A., & Friedlander, A. M. (2006). Effects of rotational closure on coral reef fishes in Waikiki-Diamond Head Fishery Management Area, Oahu, Hawaii. Marine Ecology Progress Series, 310, 139–149. http://www.jstor.org/stable/24870014

Institute of Oceanography and Fisheries (2011). Assessment of the condition of the coastal fishing resources of the Lastovsko otočje nature park. In 2010-2011