Sustainability or fun? Recreational angling in Marine Protected Areas

The study was conducted between August 2016 and July 2017 in the Akyaka MPA, in the southwestern part of Turkey (Figure 1). The Akyaka MPA is located on the eastern side of Gökova Bay, which includes a lagoon area. The shore is mostly rocky and this feature makes the Gökova shore a sheltered area for juveniles of most species. On the other hand, in terms of fisheries, longlines, trammel nets and gillnets are commonly used in Gökova Bay (Ceyhan et al. 2009; Dereli et al. 2015). Gökova Bay is also a favorite fishing area for recreational fishers. Handline, demersal and pelagic jigs are prevalent techniques among recreational anglers.

Samples were collected monthly (two days on mid-month weekends; 12 months in total). The largest number of angler visits was observed on weekends. Therefore, the time and day of sampling were selected accordingly. The daily number of anglers was recorded for each sampling day. The sampling area has estuary characteristics. Most anglers perform on rocky and sandy substrates. Fishing tackle was designed according to the angling gear of other local daily anglers (i.e. anglers were mimicked; Fig. 2). Breadcrumbs were used as bait. Each sampling event started 3 h before sunset and was completed within 2 h. Sampling depths ranged from 1 and 3 m.

Figure 2

Captured individuals were brought to the laboratory in ice and identified to the species level. Total length was measured to the nearest 0.1 cm and weight was determined to the nearest 0.01 g.

Daily CPUE (kg angler⁻¹ day⁻¹) was determined according to the following formula (Aydın 2011): CPUE=∑Weight(kg)∑RecreationalAngler×∑FishingTrials(day)CPUE = \frac{{\sum {Weight(kg)} }}{{\sum {\user1{Recreational} \times \sum {FishingTrials(day)} } }}

Species caught were also categorized into commercial and non-commercial. Length at first maturity of each species (L_m or L₅₀) was obtained from scientific papers on a given species (Supplementary Table S1) and total lengths were compared with length at first maturity and minimum landing sizes (MLS) for commercial species. According to the Turkish Commercial Fishery Communique, four of the commercial species caught have length restrictions: Pagellus erythrinus – 15 cm, Dentex dentex – 35 cm, Diplodus vulgaris – 18 cm and Diplodus sargus – 21 cm. To understand the indirect potential impact on commercial fisheries, future landings of D. vulgaris were estimated as an example. First, the minimum size of a captured individual (6.3 cm) was considered to be at the level of length at first maturity (L_m = 13 cm). Second, that individual was considered to be of minimum landing size (MLS = 18 cm). The same numerical difference between the smallest size and L_m (+ 6.7 cm) and the smallest size and MLS (+ 11.7 cm) was added to the length of all individuals. L_m (13 cm) and MLS (18 cm) values were obtained from Soykan et al. (2015) and the Turkish Fishery Communique, respectively.

Ricker’s (1975) formula was used to estimate the weight of all individuals that corresponds to at/after L_m and MLS: W=a×LbW = a \times L^b

Length–weight relationship estimates were performed in Microsoft Excel (Microsoft Corporation 2018) and RStudio was used for visualization (RStudio Team 2015).

The projection of future landings of D. vulgaris was analyzed based on the determined length–weight relationships. The results of the non-linear regression are presented in Table 3. The b value (3.10) for D. vulgaris was compared with the b value (3.03) for the same species obtained in the previous study (Akyol et al. 2007) conducted in the Gökova Bay fishing ground. Due to the differences in sample sizes, differences between b values were not considered significant. The b value for D. vulgaris in the present study is slightly above 3 (i.e. isometric length–weight relationships), but not significantly different from the cubic value. Therefore, it can be assumed that the projection (at and after L_m and MLS) is reliable. Estimated weights of individuals were projected for length at maturity and MLS, respectively (Figure 3).

Figure 3

According to the results of the study, the maximum lengths of most of the species were below maturity lengths or minimum landing sizes (Supplementary Table S1). The presence of juveniles in the catch contradicts the ecosystem-based fisheries management. Harvesting unprotected immature individuals in their early life stages may prevent the spillover of species to exploitable legal fishery grounds. Therefore, recreational angling may have a negative impact on the sustainability of local stocks.

Many Sparidae species inhabit lagoon areas (e.g. D. annularis, D. vulgaris, D. sargus, S. salpa) and hard seabed (Acarlı et al. 2009; Garcia-Rubies & Macpherson 1995). The shore of the Akyaka MPA has rocky substrates that are frequently used by recreational anglers. According to the results of the present study, Sparidae species caught from the rocky substrate accounted for 40.64% of the total catch.

A total of 12 individuals of D. vulgaris were caught in the present study (≈ 160 g). According to the length–weight projection, if D. vulgaris could be fished based on length at first maturity, it would reach almost five times the weight (≈ 800 g) of the sample. Thus, for length at first maturity, the MLS of D. vulgaris was above the maximum catch length of the sampled individuals. This clearly indicates that shore angling in the Akyaka MPA is unsustainable and an unsuitable fishing method for this area. The projection showed that ≈ 1900 g fish could be caught if the total length of individuals was above MLS. Furthermore, D. vulgaris landings based on the actual and extrapolated data were 0.6 kg and 8 kg per angler per year, respectively (Table 4). MSLs (Minimum Size Limits) become useful if the growth exceeds losses due to natural mortality and by-catch mortality (injuries caused by capture, handling, thermal stress, depth change, and predation). Therefore, size limits are a valuable tool to avoid catching small fish (Bohnsack 2000).

The projection presented is exactly in line with Bohnsack’s (2000) statement: “MSLs (minimum size limits) are intended to provide long-term benefits to fisheries by allowing juveniles to escape fishing mortality so that they can enter the fishery later at larger size. NTRs (No Take Reserves) are intended to provide similar benefits by increasing the supply of recruits and exporting fishes to surrounding fishing grounds”.

Positive effects of conservation measures can be clearly understood from some observational studies. According to Harrison et al. (2012), marine reserves directly support fish and fishers. Roberts & Hawkins (2000) found that there are eight different fishing types in the area adjacent to the De Hoop Marine Protected Area (South Africa), and the De Hoop reserve provides protection to over 60 exploited species. According to Halpern (2003), density, biomass, size, and diversity of carnivorous, herbivorous, and planktivorous fish, as well as of invertebrate feeders and invertebrates are higher inside the reserves than outside. If the Akyaka MPA is properly managed under the conservation objectives, the contribution of fish and other organisms to commercial fishing grounds could be higher than at present.

On the other hand, banning the towed gear in MPAs provides an opportunity to increase species biomass (Fisher & Frank 2002). However, permitting recreational angling does not comply with the area closure management approach (Schroeder & Love 2002). Gökova Bay has an advantage due to trawl and purse seine restrictions. These restrictions are sound implementations, but shore angling may impede the recovery of the MPA and spillover of species to fishery grounds. The indirect effect of recreational anglers on the spillover of species may only become apparent over a long period of time. Commercial fishers target a large percentage of species caught by recreational fishers, and recreational fishers affect the catch of commercial fishers and their income (Font et al. 2012).

Common findings on recreational angling pressure were presented in some related studies on MPAs or NTZs. According to Schroeder & Love (2002), the primary source of fishing mortality is recreational angling. In this context, Venturini et al. (2017) determined the impact of recreational angling on fish stocks. They revealed contradictions with the law and the minimum catch size (in terms of first reproduction size). The interesting finding in their study was that NTZs (where the spillover effect occurs) attracted anglers and the gross harvest of anglers in their study area accounted for 8% of the total yield of the small-scale fishery.

According to the Turkish amateur fishery communique, amateur fishery is defined as: “a fishing activity carried out by a fisherman for recreation, sport, or professional purposes, other than making any monetary profit or selling fish” (GDFA 2020). Therefore, amateur and recreational fishing are considered in the same sense in Turkey. However, small-scale fishing competes with large-scale and recreational fishing in Gökova Bay, and the exact number of recreational fishers is not known (Ünal et al. 2019). Angling (both from shore and boat) and spearfishing are the most preferred amateur fishing techniques in Gökova Bay (Ünal & Erdem 2009). Ünal & Erdem (2009) identified ten species in amateur fishing in Gökova Inner Bay: Pagellus erythrinus, Mugil sp., Sparus aurata, Dicentrarchus labrax, Diplodus vulgaris, Lichia amia, Epinephelus sp., Mullus sp., Trachurus sp. and Euthynnus alletteratus. In addition to these species, Pomatomus saltatrix, Sphyraena sphyraena and Octopus vulgaris are also caught. Moreover, they concluded that amateur fishers may impact small-scale fisheries. On the other hand, Dereli et al. (2015) reported a decline in local fish resources in small-scale fisheries in Gökova Bay. They found that the average catch was 15.5 kg·boat⁻¹·day⁻¹ for gillnet fishers and 5.2 kg·boat⁻¹·day⁻¹ for longline fishers in this area. In personal interviews, recreational fishers who participated in daily boat fishing tours were asked about capture statistics, and their catch ranged between 2–7 kg·angler⁻¹·day⁻¹ (C. Bulut, personal communications). They proposed a more efficient protection of NTZs from all fishing activities. The results of the present study showed that the approximate yield of recreational angling on the shore of the Akyaka MPA was 0.328 kg. However, if daily catch is estimated using a simple equation, total landing reaches about 1705 kg in the Akyaka MPA (Table 2) and this is considerably high for recreational fishing. This finding may indicate a negative impact of recreational angling on fish stocks.

No studies on spillover have been conducted in the Gökova MPAs. However, results of previous projects showed that the spillover effect may occur in the Akyaka MPA. The first biodiversity study in the Akyaka MPA was conducted in 2010 by the General Directorate of Fisheries and Aquaculture, Turkey. Turkey Ecological Research Society (EKAD, 2013) conducted a second biodiversity study in 2013 and found that there were more fish species in the Akyaka MPA than in other areas. It was observed that while the maximum lengths of five species (D. annularis, S. lessepsianus, P. erythrinus, B. boops, S. rivulatus) increased, the maximum lengths of four species (P. incisus, D. vulgaris, D. dentex, L. aurata) decreased. The decrease in maximum lengths in the Akyaka MPA may indicate the existence of a nursery habitat and a spillover effect. According to the results of the present study, many fish do not reach the length at first maturity and have the potential to spread into fishery grounds. Therefore, it may be considered that recreational angling has a negative impact on the spillover effect.

Marine and freshwater species have similar mortality rates in catch-and-release fishing (CRF). Fish mortality rates in CRF are affected by hooking location, natural bait, deep hooking, use of “J” or circle hooks, water depth and temperature, playing and handling times. Regarding hook types, barbless hooks result in lower fish mortality than barbed hooks (Bartholomew & Bohnsack 2005). Aalbers et al. (2004) reported that all mortalities occurred within five days of release (i.e. released fish may have a low survival). Logically, the occurrence of release mortality is inconsistent with NTZ objectives (Bartholomew & Bohnsack 2005). As regards hook types and fishing gear manipulation, all recreational fishers in the Akyaka MPA use barbed hooks. Furthermore, it has been observed that some anglers do not use their hands in the process of removing fish from hooks, especially if they do not know what they caught, and instead they step on the fish with one foot to remove a hook and then release it. This manipulation may potentially significantly increase fish mortality. Therefore, CRF should not be considered a good option for shore angling in the Akyaka MPA. In this regard, lack of education among anglers was identified as the major shortfall. People need to be educated about marine life to ensure that mortality is reduced.

On the other hand, Sale et al. (2005) argued that too many MPAs are located in the wrong places. According to the present study, although the Akyaka MPA was established in the right place (i.e. near the lagoon), the presence of juveniles in the recreational catch indicates that this area is not properly managed. Partial protection may have benefits (like trawl restrictions for habitat protection), however, partially protected areas are not as effective as NTRs (Sala & Giakoumi 2018). More comprehensive protection plans should be put into effect.

In addition to all the above methods, lure fishing has also been observed in the Akyaka MPA. Anglers who use this method, target fish such as D. labrax, S. sphyraena, P. saltatrix etc. However, there are no data on lure fishing on the shore of Gökova Bay. Micheli et al. (2005) reported that the size and abundance of predatory fish species targeted by local fisheries were greater in NTRs than in exploited areas. Other than recreational angling, lure fishing may have a potential negative effect on spawning stock biomass in the Akyaka MPA.

Although recreational fishing is not a commercial activity (i.e. no fish are sold), it makes a significant economic contribution to other fisheries-related sectors (by spending money on food, bait, accommodation, travel, boat fuel, boat maintenance and fishing gear costs; Tunca et al. 2013). However, this economic contribution depends on sustainability of fish stocks (i.e. importance of juveniles).

Samples for the study were collected using simple fishing tackle that any angler can purchase. This easy access may lead to increased potential of recreational angling and may increase the pressure on juveniles. As mentioned in various studies on juveniles, the sustainability of fish stocks depends on recruitment success. In addition, negative effects of lost fishing gear that originates from recreational angling should not be ignored.

Therefore, the following conclusions can be made:

Juveniles should be protected and the spillover effect should not be prevented to ensure the spread of species to fishery grounds; this strategy may potentially have a large economic contribution to local fisheries in the future;